PATHOLOGY AND INTERVENTION

IN MUSCULOSKELETAL REHABILITATION

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PATHOLOGY

AND INTERVENTION

IN MUSCULOSKELETAL

REHABILITATION

Editors

David J. Magee, PT, PhD Professor and Associate Dean

Department of Physical Therapy

Faculty of Rehabilitation Medicine

University of Alberta

Edmonton, Alberta, Canada

James E. Zachazewski, PT, OPT, SCS, ATC Clinical Director

Physical Therapy

Massachusetts General Hospital

Boston, Massachusetts

William S. Quillen, PT, PhD, SCS, FACSM Professor

Associate Dean, College of Medicine

Director, School of Physical Therapy and Rehabilitation Sciences

University of South Florida

Tampa, Florida

Editorial Consultant

Bev Evjen Swift Current, Saskatchewan, Canada

ELSEVIER

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PATHOLOGY AND INTERVENTION IN MUSCULOSKELETAL REHABILITATION ISBN: 978- 1-4160-0251-2

Copyright © 2009 by Saunders, an imprint of Elsevier Inc. Photo Copyright © 2009 for Chapter 8 and Chapter 14, will be retained by Diane Lee Photo Copyright © 2009 for Chapter 8 and Chapter 14, will be retained by Linda-Joy Lee

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PATULonMORAL JOINT Christopher M. Powers, Richard B. Souza, and John P. Fulkerson

Introduction

Disorders of the patellofemoral joint are among the most perplexing and clinically challenging conditions encoun­tered in musculoskeletal practice . Patellofemoral pain (PFP) is one of the most common disorders of the knee, affecting as many as 22% of the general population reporting symptoms. 1 Patellofemoral-related problems are prevalent in a wide range of individuals, but the highest incidence is seen in physically active people, such as runners, tennis players, and military recruits.2- 6 In general, the incidence of patellofemoral-related problems is higher in females (2 : 1); however, among athletes, the incidence is higher in males (4: 1 ) . 1

Despite the higb incidence of PFP in the general popu­lation, the pathophysiology of this disorder is sometimes elusive. This is supported by the fact that no clear consen­sus exists on how PFP should be treated . For example, a myriad of conservative procedures have been advocated (e .g. , bracing, taping, foot orthotics, strengthening, stretch­ing), 1 ,7- 14 and numerous surgical techniques have been described I 5- 2 1 Initial ly, nonoperative care is preferred, but surgical intervention is considered if conservative care fails.22 Although nonoperative care appears to be successful in the short term/, 2 3 the long-term results are less com­pelling. 14,24,25 A systematic review of 20 randomized, controlled trials evaluating various forms of conservative interventions for PFP revealed that only eight reported a positive outcome.26 From a surgical standpoint, the success rates for patellofemoral-related procedures are con­sidered equivocally poor compared to other orthopedic

. 22 operations. The difficulty involved in treating PFP reflects the com­

plexity of the patellofemoral joint and the multifactorial nature of the disorder. To treat tllls condition effectively, the clinician must clearly identify the primary cause or causes of the pain. The purpose of this chapter is to provide the reader with an understanding of the relevant anatomy,

kinesiology, and biomechanics of the patellofemoral joint and to review current theories related to the etiology of PFP, evaluation methods, and treatment strategies.

Functional Anatomy

The patellofemoral joint consists of the articulation of the patella and the trochlear surface of the femur. It is an inte­gral part of the knee extensor mechanism, and as such it plays a key role in normal knee function and lower extl-em­ity biomechanics. The ability of the patellofemoral joint to improve the mechanical efficiency of the extensor mecha­nism and to accept and redirect forces depends on a host of factors, including the joint's osseous structure and con­tributions from various soft: tissues, such as the quadriceps musculature, quadriceps tendon, patellar tendon, and reti­naculum. Clinicians must have an understanding of the anatomical structure of tl1is joint to appreciate both normal and pathological function.

Osseous Structure

Patella Contained within the quadriceps tendon, the patella has the distinction of being the largest sesamoid bone in the body. 1

The patella consists primarily of cancellous bone covered by thin, compact I an1 ina; its axial length is approximately 4 to 4.5 cm ( 1 .6 to 1 .8 inches), and it is approximately 5 to 5.5 cm (2 to 2 .2 inches) wide. The thickness of the patella varies considerably, attaining a maximum height of 2 to 2 .5 cm (0.77 to 1 inch) at its central portion.27

The articular surface of the patella is divided into the medial and lateral facets by a vertical ridge ( median ridge) that roughly bisects the patella ( Figure 1 8 _ 1 ) 28 The lateral facet often is slightly larger than the medial facet 29 The medial facet is subdivided by a less prominent vertical ridge tlut separates the medial facet proper and the smaller, odd facet (see Figure 18- 1) . The articulating surfaces of the

601

602 C HAPTER 1 8 • Patellofemoral Joint

./ Superior Medial � articular facets x/-:�

If

If \- Lateral

( r --- \ ,,",",,dao,"

Odd� �

' � Inferior Figure 18-1 Articular facets of the patella.

patella are covered widl aneural hyaline cartilage, the thick­est cartilage in the body.30 Maximum cartilage iliickness is found at dle central portion of the patella (approximately 4-5 mm) and decreases from ilie median ridge to the medial and lateral borders.

Trochlear Surface of the Femur The femoral condyles form the trochlear groove that provides the articulating surface of ilie femur. Similar to the articular surface of the patella, ilie trochlear surface is divided into medial and lateral facets, the lateral facet being larger and extending more proximally and anteriorly dlan its medial counterpart ( Figure 1 8-2 ) . This orientation of the lateral femoral condyle provides a bony buttress dlat helps provide lateral patellar stability.3 1 The trochlear groove is shallower proximally than distally, indicating iliat bony stability is compromised as ilie patella moves superi­orly during terminal knee extension . The cartilage covering ilie trochlear surface of the femur is much iliinner ilian iliat covering the patella ( i .e . , 2 to 3 mm).30

Soft Tissue Structures

Synovium The synovial lining of dle patellofemoral joint, which is essentially the synovium of the anterior portion of ilie knee, has three components: the suprapatellar synovium, ilie peri­patellar synovium, and ilie infrapateUar synovium. These

Lateral condyle --+--

Intercondylar notch Figure 18-2 Inferior aspect of the distal end of the femur.

---++- Medial condyle

iliree portions blend imperceptibly with each oilier, allow­ing free communication wiili the knee joint proper.32 The peripateLlar synovium creates a small synovial fold or fringe less ilian 1 cm (0.5 inch) wide that surrounds ilie patella; this generally is regarded as the true synovium of the patello­femoral joint.3o Inflammation or scarring of iliis synovial fold ( i .e . , plica) can produce symptoms similar to those of cartilage degeneration, and iliis type of inflammation or scarring is commonly associated with chondromalacia. 33

Portions of the Synovial Lining of the Patellofemoral Joint

• Suprapatellar synovium (pouch)

• Peri patellar synovium (plica)

• Infrapatellar synovium

Fat Pads Three fat pads occupy the anterior knee: the quadriceps fat pad, the prefemoral fat pad, and the infrapatellar fat pad ( Figure 1 8_ 3 ) .34 The infrapatellar fat pad, or Hoffa's fat pad, is ilie largest fat pad in the region and has been studied extensively because of its proposed role in various patholo­gies. 34-38 It is a voluminous structure located just inferior to the infrapatellar pole.35 It extends inferiorly to the deep infrapatellar bursa at the insertion of the patellar ligament into ilie tibial tuberosity. Hoffa's fat pad attaches to several structures, including ilie intercondylar notch via the liga­mentum mucosum, ilie patellar tendon, ilie inferior pole

. I f d · ·34 of ilie patella, and dle antenor loms 0 le mel11SCl.

Figure 18-3 Sagittal MRI scan of the knee showing the fat pads that occupy the

anterior aspect of the knee.

The quadriceps fat pad, also known as the anterior

suprapatellar fat pad, lies superior to the suprapatellar pole between the distal quadriceps tendon anteriorly and the suprapatellar recess posteriorly.39 Just deep (posterior) to the suprapatellar recess and the suprapatellar bursa is the prefemoral fat pad, which is anterior to the femoral shaft and superior trochlear groove.40

Fat Pads of the Patellofemoral Joint

• lnfrapatellar (Hoffa's) fat pad

• Quadriceps (anterior suprapatellar) fat pad

• Prefemoral fat pad

The fat pads of the knee house neurovascular projec­tions. The infrapatellar fat pad is highly vascularized and highly innervated. Terminal extensions of the inferior geni­cular arteries anastomose in the infrapatellar fat pad, richly supplying it and its synovial coverings. 37 Substance P immunoreactive pain fibers are widespread and equally distributed ·,hroughout the fat pad, retinaculum, and synovium.38

Several functions have been proposed for the fat pads, including secretion of synovial fluid, occupation of dead space, and joint stability. Current research concludes that the infrapatellar fat pad appears to play a role in biomechan­ical support and neurovascular supply to the adjacent structures 34

Functions of Fat Pads

• Synovial fluid secretion

• Occupiers of dead space

• Joint stability

• Neurovascular supply

Figure 18-4 Active and passive soft tissue stabilizers of the patella. ( Redrawn

from Fulkerson JP, Hungerford DS: Disorders of the patellofemoral

joint, cd 2, Baltimore, 1990, Williams & Wilkins.)

Patellofemoral Joint • CHAPTER 18 603

Soft Tissue Stabilizers

Because the patellofemoral joint lacks a tightly closed cap­sule, external assistance is required to achieve patellar stabil­ity within the trochlear groove; this assistance is provided by soft tissue stabilizers. In general, the soft tissue stabili­zers of the patellofemoral joint can be described as passive stabilizers or active stabilizers.

Passive Stabilizers Passive stabilizing structures include the patellar tendon infe­riorly and the medial and lateral retinaculum (Figure 1 8-4) . The patellar tendon functions to transmit the forces gener­ated by quadriceps contraction to the tibia. This structure typically is oriented slightly lateral Witll respect to tile long axis of the tibia, tllereby creating a slight lateral pull on the patella.3o

Passive Patellar Stabilizers

• Patellar tendon

• Medial retinaculum

• Lateral retinaculum

A normal patellar retinaculum consists oflayered, fibrous connective tissue tllat traverses the medial and lateral mar­gins of the patella with attachments to the femur, tibia, patella, and patellar ligament.4 1 The superficial fibers of the retinaculum originate frolll tile vastus lateralis and vastus medialis fascia, linking the quadriceps to the patella (Figure 1 8_ 5 ) . 30,4 1 This linkage is responsible for the dynamic influence of tile quadriceps on the patellofemoral joint during active knee motion.

The lateral retinacululll is composed of two distinct portions, a thinner superficial layer and a thicker deep layer. The deep layer is further divided into three fibrous components: the epicondylopatellar band (or lateral

Lateral retinaculum, vastus lateralis,

and iliotibial tract

Quadriceps

Medial retinaculum and vastus medialis

604 CHAPTER 1 8 • Patellofemoral Joint

Figure 18-5 Cadaveric dissection showing interdigitation of the quadriceps musculature and iliotibial band with the peripatellar retinaculum.

VM, Vastus medialis; RF, rectus femoris; P, patella; VL, vaShlS

lateral is; ITB, iliotibial band; LR, lateral retinaculum; MR, medial

retinaculum.

patellofemoral ligament), the deep transverse retinaculum,

and the patellotibial band (Figure 1 8-6) . These structures connect the patella to the iliotibial band ( ITB ) and help prevent medial patellar excursion.42 Because most of the lateral retinaculum originates from the ITB, th.is structure is drawn posteriorly with knee flexion, placing a lateral force on the patella.43

The medial retinaculum forms a tough, fibrous layer that helps to limit lateral patellar excursion . The lateral retinacu­lum usually is thicker than the medial retinaculum and gen­erally is accepted as providing stronger lateral support.44

The specific role of the peripatellar retinaculum as a frontal plane stabilizer of the patellofemoral joint has been well established.45- 48 However, because of its unique orien­tation, the peri patellar retinaculum plays a complementary load-sharing role with respect to the patellar ligament by resisting tensile forces created by the extensor mecha­nism.45, 49 Similar to the patellar ligament, the patellar reti­naculum provides distal inferior support for the patella through the medial and lateral meniscopatellar ligaments, which connect the patella to the tibia.46

The lateral retinaculum contains small nerve endings, which suggests that this structure can be a source of symp­toms.3D In addition, Sanchis-Alfonso et al .5D reported on the widespread presence of substance P in this area. Fulkerson et al.5 1 found that nerve injury in the lateral retinaculum can be a source of pain and may be related to chronic tightness.

Active Stabilizers Active stabilizers of the patella consist of the four heads of the quadriceps femoris muscle (the vastus lateralis, vastus medialis, vastus intermedius, and rectus femoris) , which

Epicondylopatellar band Vastus lateralis

/ Lateral joint line

Figure 18-6

Fibrous expansion of vastus lateralis

Patellotibial band Tibial tubercle

Superficial oblique retinaculum

Anatomy of the lateral extensor mechanism and retinaculum showing the orientation of the elements that

make up the superficial and deep layers. ( Redrawn from Fulkerson JP, Gossling R R: Anatomy of the knee

joint later·al retinaculum, Clin Orthop 153:183-188, 1990.)

Active Patellar Stabilizers

• Vastus lateralis

• Vastus intermedius

• Vastus medialis

• Rectus femoris

fuse distally to form the quadriceps tendon . These muscles, which can be identified at their insertion into the patella, provide dynamic control of the patellofemoral joint.

The rectus femoris (RF) inserts into the anterior por­tion of the superior aspect of the patella, with the super­ficial fibers continuing over the superior aspect of the patella and ending in the patellar tendon. The vastus inter­medius (VI) inserts posteriorly into the base of the patella but anterior to the joint capsule . Both the vastus lateralis (VL) and vastus medialis (VM) insert into their respective sides of the patella and reinforce the medial and lateral retinaculum.52, 53

The lower fibers of the VM insert more distally on the patella and ;>.t a greater angle from the vertical compared to the VL. In a detailed anatomical analysis, Lieb and Perrl4 determined the angle of insertion of the various heads of the quadriceps muscle with respect to the vertical axis. The fiber alignment in the frontal plane was as follows: VL, 12° to 1 5° laterally; RF, r to 10° medially; and VM,

• upper fibers, 1 5° to 1 8° medially, lower fibers, 50° to 55° medially (Figure 1 8-7) . The fibers of the VI were found to lie parallel to the shaft of the femur.

The distinct and abrupt change in the fiber orientation between the superior and inferior portions of the vastus medialis led Lieb and Perry54 to consider each of these por­tions as a separate entity in their mechanical study. The lower fibers were designated the rastus medialis oblique

(VMO) and the upper fibers the vastus medialis longus (VML). The fiber orientation of the VMO makes this struc­ture particularly effective in providing medial patellar stability. 54

As a result of the posterior origin of the vasti ( linea aspera), any quadriceps muscle contraction ( regardless of knee flexion angle) results in compressive forces acting on the patellofemoral joint. Even when the knee is fully extended, substantial joint compression can occur. The posterior angulation of the vastus medialis and vastus later­aJis fibers has been reported as approximately 55° from the vertical. 55

In summary, the bony confines of the trochlea combined with the passive and active soft tissue stabilizers define the limit of patellar excursion and contribute significantly to stability of the ratellofemoral joint. The balance between medial and lateral stability is essential for maintaining ap­propriate alignment of the extensor mechanism and normal biomechanics of the patellofemoral joint.

Patellofemoral Joint • CHAPTER 1 8 605

Vastus lateralis

Iliotibial band ----'�'i\.��

Lateral retinaculum -r"ffil'!f*'vI

Figure 18-7

Vastus medialis longus

50-55°

Vastus medialis oblique

Medial retinaculum

Components of the quadriceps-femoris complex. Notc the angle of

insertion of the various components of the complex. The orientation

of the muscle fibers dictates the line of action and the pull on the

patella. ( Modified from McConnell ], Fulkerson J : The knee:

patellofemoral and soft tissue injuries. [n Zachazewski J E, Magee D J, Quillen WS, editors: Athletic injUl'ies and rehabilitation, p 697,

Philadelphia, 1996, WE Saunders . )

Kinesiology

The complexity of the patellofemoral lies in its dynamic characteristics. Therefore clinicians must understand the normal patellofemoral joint motions before they can deter­mine whether abnormal joint motion is present.

Normal Patellar Kinematics

Inability to visualize the relationship between the patella and the trochlear groove makes clinical assessment of patellar tracking an imprecise task. Also, identifying abnormal patellar motion is difficult if "normal" patellar tracking has not been clearly defined. Kinematic magnetic resonance imaging (KMRI ) has been used to quantify patellar movement during resisted knee extension from

606 C HAPTER 1 8 • Patellofemoral Joint

45° flexion to full knee extension (0°). 56, 57 Assessment of patellar kinematics in this arc of knee motion is clinically relevant, because this is the range in which tracking abnormalities occur. KMRI has a distinct advantage over static imaging procedures in that the contribution of the extensor mechanism to patellofemoral joint kinematics can be assessed .57

Frontal Plane Movements The normal position of the patella is slight lateral displace­ment throughout knee flexion and extension. The normal pattern of patellar motion in the frontal plane is character­ized by slight medial displacement from 45° to 15° knee flexion, followed by slight lateral displacement at the end range of extension ( 15° to 0°).58 This motion has been described previously as the C-curve pattern .59 The estimated amount of medial and lateral movement is about 3 mm in each direction based on quantitative analysis.58 Qualita­tively, with this movement pattern, the patella appears to be evenly centered in the femoral trochlear groove throughout this range of motion. 58

The tendency of the patella to displace medially during knee extension is related to the geometry of the femoral trochlear groove . Because the lateral femoral condyle typically is larger and projects farther anteriorly than the medial condyle, the trochlear surface is angled slightly medially when viewed from distal to proximal positions.6o

I n addition, the shift from medial to lateral patellar motions starting at 1 8° flexion can be explained by the screw home mechanism of the knee. During terminal extension of the non-weight-bearing knee, the tibia rotates laterally as a result of the unequal curvature between the femoral condyles 6 1 As was demonstrated by van Kampen and Huiskes,60 patellar motion is highly influenced by rotation of the tibia, and lateral rotation induces a lateral patellar displacement.

Transverse Plane Movements During knee extension from 45° to 0° , the patella tilts medially (5° to 7°) from a laterally tilted position Of l oo.58

As with medial and lateral patellar displacement, this motion pattern appears to be related to tlle geometry of the femoral trochlear groove .58 Again, from a qualitative consideration, this movement pattern gives the patella me appearance of being evenly centered in the femoral trochlear groove throughout this range of motion .58 The fact that me patella typically is lateral to the midline and laterally tilted throughout knee extension suggests tllat patellar malalign­ment is more a problem of degree rather than position.

Sagittal Plane Movements The motions of the patella in the sagittal plane consist of flexion and extension . Flexion is defined as the motion in which me inferior pole of the patella moves posteriorly, whereas extension is defined as the motion in which the inferior pole moves anteriorly. Flexion of the patella occurs in conjunction with knee flexion; however, the magnitude of patellar flexion is about 20° less than that of knee flex­ion.6o For example, when tlle knee is flexed to 60° , me patella typically is flexed to 40° . Similarly, as the knee extends, the patella also extends from the flexed position.6o

Patellofemoral Joint Contact Area

During knee flexion, me patella moves from the superior (shallower) portion of tlle trochlear groove to the inferior (deeper) portion.58 As such, the articulating surface of the patella on the femur varies mroughout me range of knee motion. Movement from full extension to 90° flexion results in a band of contact that moves from the inferior to me superior pole of me patella (Figure 18_8).62 Nor­mally, the odd facet makes no contact during tlus range. Between 90° and 1 35°, me patella rotates laterally witll

Figure 18-8 Odd facet Odd facet Contact area patterns on the patella as a function of

the knee flexion angle. In general , contact area

increases with increasing knee flexion. L, Lateral;

M L

�Oddfacet

�� L M

M, medial. (From McConnell ], Fulkerson J: The

knee: patellofemoral and soft tissue injuries. In

Zachazewski ]E, Magee DJ , Quillen WS, editors:

Athletic injuries and rehabilitation, p 694,

Philadelphia, 1 996, WE Saunders . )

the ridge between the medial and odd facets, making con­tact with the medial condyle. At 1 35° , the odd facet and the lateral portion of the lateral facet make contact, as does the quadriceps tendon (see Figure 1 8_8 ) .62

Because the patella enters the deeper portion of the trochlear groove during knee flexion, the area of contact between the patella and the trochlear groove increases. In fact, the patellofemoral contact area has been reported to increase threefold, from 0 .8 cm2 (0 . 12 in2 ) at 0° to a maximum of 2 .4 cm2 (0.4 in2 ) at 60° . 55 This increase in contact area with increased knee flexion functionally serves to distribute joint forces over a greater surface area, thereby minimizing joint stress.

Frontal Plane Influences

Fulkerson and Hungerford30 described the natural ten­dency of the patella to track laterally as the "law of valgus." This tendency is a result of the valgus orientation of the lower extremity. As the quadriceps muscle follows the lon­gitudinal axis of the femur, the quadriceps angle (Q angle) is formed, creating a lateral force vector that acts on the patella (Figure 1 8-9) . This predisposes the patella to lateral tracking forces with quadriceps muscle tension.63

Figure 18-9 The orientation of the quadriceps force vector and patellar ligament force vectors creates a lateral force acting on the patella. (From Powers

eM: The influence of altered lower-extremity kinematics on

patellofemoral joint dysfunction: a theoretical perspective, ] Orthop

Sports Phys Ther 33:639-646, 2003.)

Patellofemoral Joint • C H APTER 1 8 607

Clinically, the Q angle is measured as the angle formed by the intersection of a line drawn from the anterosuperior iliac spine (ASIS) to the midpoint of the patella and a prox­imal extension of a line drawn from the tibial tubercle to the midpoint of the patella.64 The Q angle is greater in women than in men because women have a wider pelvis; the average Q angle is 15° to 18° in women and approximately 12° in men.3 1 This variation between the genders may partly explain the higher incidence of PFP in females, because a larger Q angle creates a larger valgus vector and therefore a potentially greater predisposition to lateral tracking.65

Joint Biomechanics

The patellofemoral joint is susceptible to the largest loads in the body.66 Because abnormal forces and stresses are thought to be a primary factor in the origin of patellofe­moral pain, it is important that clinicians understand the normal biomechanics of this joint.

Function of the Patella

The primary function of the patella is to facilitate knee extension.6 1 This mechanical attribute has been described in detail and has been shown to increase the functional lever arm of the extensor mechanism.67 Documentation of strength losses in subjects who have undergone patellect­omy supports this concept. Fletcher et al.68 reported a 49% reduction in the torque output of the extensor mechanism after patellectomy.

Functions of the Patella

• Improve the efficiency of the last 30° of extension

• Guide the quadriceps (patellar) tendon

• Reduce friction in the quadriceps mechanism

• Facilitate transmission of quadriceps forces

• Control (through the quadriceps) capsular tension in the knee

• Act as a bony shield

• Improve the esthetic appearance of the knee

The quadriceps muscle lever arm varies throughout the knee range of motion, with reported maximum values ranging from 4.9 cm ( 1 .9 inches) at 30° flexion69 to 7 .8 cm ( 3 . 1 inches) at 15° flexion?O The effectiveness of the patella diminishes with full flexion because the patella sinks into the trochlear groove, reducing the anterior dis­placement of the quadriceps tendon. The extensor lever arm is only slightly reduced with full extension (4.4 cm [ 1 .7 inches ] ) .69

Apart from improving the moment arm of the quadriceps muscle, tlle patella provides protection for the articular car­tilage of the trochlea and prevents excessive friction between the quadriceps tendon and the femoral condyles, permitting

608 C HAPTER 1 8 • Patellofemoral Joint

the patellofemoral joint to tolerate high compressive loads. The patella also acts as a guide for the converging heads of the quadriceps muscle, facilitating transmission of the muscular forces to the patellar tendon.67

Patellofemoral Joint Reaction Force

Because the quadriceps is the only muscle to cross the patel­lofemoral joint, the patellofemoral joint reaction force (PFJRF) is determined quasi-statically by the force and moment balance of the quadriceps force vector and the patellar ligament force vector.71 Early biomechanical descriptions of the patellofemoral joint characterized this articulation as a frictionless pulley where the patellar liga­ment force (Frd was assumed to be equal to the force applied by quadriceps tendon (FQ).72,73 However, sub­sequent experimental studies and mathematical representa­tions of the patellofemoral joint suggested that the patella also acts as a lever, thereby creating a force differential between the quadriceps tendon and the patellar liga­ment.71,74 This force differential is thought to occur as a result of the varying geometry and shape of the distal femur and patella, as well as the changing point of contact between the patella and femur as the knee flexes and extends.

The PFJRF is the measurement of compression of the patella against the femur, and it depends on the angle of knee flexion, as well as muscle tension?5 The resultant of the quadriceps muscle force vector and the patellar tendon force vector is equal and opposite to the PFJRF, which evokes compressive stresses on the patellofemoral articular cartilage (Figure 18-10).76 Previous investigations have

Figure 18-10 The patellofemoral joint reaction force increases as a fimction of

quadriceps force and knee angle. Fq, Force of the quadriceps tendon;

Fp, force of the patellar tendon; R, patellofemoral joint reaction force.

(From McConnell J, Fulkerson J: The knee: patellofemoral and soft

tissue injuries. In Zachazewski JE, Magee D J , Quillen WS, editors:

Athletic illjuries and rehabilitation, p 700, Phjladelphia, 1 996, WE

Sau nders. )

indicated that the PFJRF for level walking is approximately 1 times body weight; it is 3.8 times body weight during stair ascent and descent77-79 and can be as high as 7 to 11 times body weight during running.8o

Patellofemoral Joint Stress

From a mechanical standpoint, patellofemoral joint stress (or pressure) is deftned as the PFJRF divided by the patel­lofemoral joint contact area. A high patellofemoral joint reaction force is not necessarily harmful to the patellofe­moral joint, because this force can be offset by a large con­tact area. However, a high joint reaction force combined with a small contact area may be detrimental.

Numerous studies have been done to measure stresses directly from cadaveric knees using pressure-sensitive film. In addition, patellofemoral joint stress has been estimated in vivo by dividing tlle estimated PFJRF by the patellofe­moral joint contact area obtained from the literature or MR!. Heino-Brechter and Powers78 reported that peak patellofemoral joint stress can vary from 2 megapascals (MPa) for level walking to 6 MPa for stair ambulation.

Pathomechanics

As mentioned, the cause of PFP can be elusive, and it may have multiple origins. For example, tissues such as the sub­chondral bone, synovium, retinaculum, and fat pad have been implicated as potential sources of patellofemoral joint symptoms.81 Excessive mechanical stresses in tllese tissu�s are believed to stimulate pain receptors. Dye8! proposed tllat differential loading of innervated tissue and the loss of tissue homeostasis may be responsible for tlle genesis of patellofemoral symptoms. In turn, restoration of tissue homeostasis (i.e., alleviation of stress in irritated tissue) is thought to reduce symptoms.

Heino-Brechter and Powers78 provided evidence sup­porting tlle concept of differential loading as a factor in the development of pain. They found that individuals with PFP experience greater amounts of patellofemoral joint stress during walking compared to pain-free controls. Because the primary goal of conservative and surgical management of PFP is to reduce pain and improve function, it is important that tlle clinician understand the mechanisms that may contribute to abnormal joint loading.

As outlined by Fredericson and Powers,82 f�ctors that con­tribute to excessive patellofemoral stress can be broken down into three categories: abnormal patellofemoral joint mechan­ics; abnormal lower extremity kinematics, and overuse.

Abnormal Patellofemoral Joint Mechanics

The signiftcance of a malaligned patella is related to the fact that, when the patella is not situated firmly in the trochlear groove, contact between the patellar and trochlear surfaces

is diminished. For example, a laterally displaced or laterally tilted patella can cause increased lateral facet stress. Two of the more common pateUofemorai joint conditions are exces­sive lateral pressure syndrome and patellar subluxation.

Excessive Lateral Pressure Syndrome Ficat et a1. 83 first described in detail the concept of excessive lateral pressure as a causative factor in patellofemoral articular cartilage pathology. These authors characterized excessive lateral pressure syndrome (ELPS) as a tilt or compression syndrome in which a laterally tilted patella increases the compression between the lateral facet and the lateral femoral condyle (Figure 1 8- 1 1 ) . This patellar posture also unloads the medial facet.

Tilting of the patella can be isolated, or it can be asso­ciated with lateral patellar subluxation.84-86 Chronic lateral tilt is determined radiologically and has been shown to have a deleterious effect on the articular cartilage. Increased density of the subchondral bone underlying the lateral facet, combined with decreased density of the medial facet subchondral bone, is a sign of the pressure differences seen in this syndrome.30

Lateral facet overload and deficient medial facet contact can lead to articular cartilage degeneration at both sites. Abnormal articular cartilage loading of the lateral facet may cross the threshold of cartilage resistance, leading fo failure.3o The primary area of lateral facet degeneration corresponds to the areas of contact in the 40° to 80° knee flexion range.87

Figure 18-1 1 Axial MRl of the patellofemoral joint showing excessive lateral tilting

of the patella, resulting in increased pressure between the lateral facet

and the lateral femoral condyle. M, Medial; L, lateral.

Patellofemoral Joint • C HAPTER 1 8 609

The mechanism of medial facet articular cartilage dam­age in ELPS appears to be different from lateral facet degeneration, because this area is susceptible to deficient contact. This form of degeneration likely can be attributed to impaired nutrition, because diminished joint compres­sion results in decreased flow of synovial f1uid.88 Seedholm et aI.87 have stated that areas of relative contact deficiency develop mild degenerative changes and are most probably asymptomatic. When combined with the shearing of the medial facet associated with lateral patellar subluxation, more extensive medial facet degeneration may occur.30

Etiology of Excessive Lateral Pressure Syndrome. The natural history of ELPS has been described as con­genital tilting of the patella followed by adaptive shortening of the lateral retinaculum. Congenital anomalies cited as possible causes of ELPS include genu varum, femoral ante­version, and dysplasia of the hip.30 The significance of a tight lateral retinaculum is dle increased posterolateral pull on dus structure with knee flexion. This, in turn, accentu­ates lateral facet compression. Insall89 stated dlat adaptive shortening of the lateral retinaculum was more likely the result of habitual lateral patellar tracking, in which the VM became stretched and the VL contracted.

Disruption of the medial stabilizers (the VM and the medial retinaculum) also has been implicated as a possible cause of ELPS.88 Ahmed et alYo conducted a mechanical study to measure the static pressure distribution on the ret­ropatellar surface. The results from 24 cadaveric specimens showed that a release of VMO tension created a pressure shift that was transferred almost entirely to the lateral facet of the patella. In addition, the change in the orientation of the pressure zone suggested a considerable frontal plane rotation of the patella relative to the femur.

Some evidence supports both theories, that the short­ened retinaculum and the insufficient dynamic medial stabi­lizers contribute to ELPS. Fulkerson et a1.91 demonstrated the effectiveness of surgical release of the lateral retinacu­lum in reducing lateral patellar tilt. Based on preoperative and postoperative computed tomography (CT) evaluation, these authors reported a mean tilt improvement of 6° at 1 0° knee flexion and I S° at 20° knee flexion. These improve­ments brought dle tilt angles of these subjects well within the normal range as demonstrated in the control group.

Douchette and Goble92 demonstrated the importance of quadriceps muscle weakness and tightness of the lateral structures as contributors to ELPS. They fOllnd a decrease in patellar tilt in patients who participated in an 8-week program of quadriceps muscle strengthening and ITB stretching. In addition, 84% of the previollsly symptomatic patients were pain free after this program.

Patellar Subluxation Patellar subluxation is abnormal medial or lateral move­ment of the patella. Abnormal patellar tracking, such that transient 'medial or lateral displacement occurs during

61 0 C HAPTER 1 8 • Patellofemoral Joint

flexion and extension, has been documented as a cause of articular cartilage damage and pain.93,94 Subluxation of the patella is differentiated from patellar instability or dislocation in that the patella stays in the trochlear groove rather than leaving it (dislocation).

In general, subluxation typically involves increased lateral displacement of the patella;30 however, medial dis­placement also can occur.95 This excessive motion results in a feeling of instability and discomfort.96 Fulkerson and Hungerford3o described three types of subluxation: minor recurrent subluxation, major recurrent subluxation, and permanent lateral subluxation. In minor recurrent subluxa­tion, the patella deviates little from its normal course; tl1is type of subluxation is not associated with clinically apparent relocation. In major recurrent subluxation, the patella comes across tl1e lateral trochlear facet and returns to the trochlear groove witl1 an audible snap. Permanent lateral subluxation is a stable lateral displacement in which there was no centering of tl1e patella.

Etiology of Lateral Patellar Subluxation. As men­tioned previously, botl1 static and dynamic structures pro­vide resistance to the inherent lateral tracking forces. Disruption of tl1e normal equilibrium of forces may lead to patellar mal alignment and associated pathology of the patellofemoral joint. To understand the etiology of a patient's PFP and to formulate an effective treatment pro­gram, the clinician must understand the specific mechanism or mechanisms involved in each patient.

Bony Abnormalities. Anatomical variations of the patella or distal femur (or both) can contribute to potential recurrent subluxation.29,97 Patellar or trochlear dysplasia compromises the inherent stability afforded by the bony structure, making tl1e patella more susceptible to laterally directed forces. Wiberg29 proposed a system for classifying patella shapes based on axial view radiographs:

• Type I: Both facets are slightly concave and symmetri­cal, and the medial and lateral facets are equal in size (Figure 1 8 - 1 2 ) .

• Type II: The medial facet is distinctly smaller tl1an the lateral facet. The lateral facet is concave, whereas the

Type I

Figure 18-12

Type II Type I I I

Classification of patellar shapes based on axial view radiographs. (From McConnell J , Fulkerson J : The knee: patellofemoral and soft tissue

injuries. [n Zachazewski JE, Magee DJ, Quillen WS, editors: Athletic

injuries and rehabilitation, p 694, Philadelphia, 1 996, WE Saunders . )

medial facet is more flat (see Figure 18- 1 2 ) . Wiberg found this to be the most common patellar shape.

• Type III: The medial facet is slightly convex and con­siderably smaller, with marked lateral facet predomi­nance (see Figure 1 8 - 12 ) . Wiberg considered this shape a frank dysplastic form.

Apart from the shape of tl1e patella, its position witl1 respect to tl1e trochlear groove can be a potential causative factor in lateral subluxation. Patella alta, as described by Insall,63 is evident when the resting position of tl1e patella is above the femoral groove (Figure 18- 13) . The high­riding patella does not sink adequately into tl1e trochlear groove with knee flexion and therefore is prone to lateral displacement.98 In addition, individuals with patella alta are predisposed to elevated joint stresses, because the contact area is minimal, particularly when tl1e knee is extended.98 Patella alta is detected witl1 1ateral radiographs, and a positive sign is a patellar tendon that is 20% longer than the patella. The excessive length of the patellar tendon is thought to be the primary cause of tl1is condition.99

Another bony etiological factor in patellar subluxation is femoral trochlear dysplasia. The trochlear groove of tl1e femur, especially the larger anterior protrusion of the lat­eral femoral condyle, provides significant bony stability for the patella. 1 00 The normal trochlear facet (sulcus) angle was established by Brattstrom lo l using a sophisticated radio­logical technique. Evaluation of 1 00 normal knees showed that the values for tl1e two genders were similar, with a mean angle of 1 43° for males and 142° for females. Higher sulcus angles represented a shallower trochlear groove and were associated with recurrent patellar subluxation.1 01,1 02 According to Hvid et a1., ' 03 a sulcus angle greater man 1 50° indicates trochlear dysplasia. Using dynamic MRI tech­niques, Powers85 reported a strong correlation ( r = 0.76) between lateral patellar displacement and me depm of tl1e trochlear groove at 0° knee flexion. This suggests tl1at troch­lear dysplasia is one of the more important etiological factors contributing to recurrent patellar subluxation.

Abnormal Skeletal Alignment. Abnormal skeletal alignments have been shown to have a profound effect on the magnitude of the Q angle and tl1e subsequent laterally directed component of the quadriceps muscle force.94,1 04 Huberti and Hayes 1 04 documented tl1e deleterious effects of an increased Q angle by measuring patellofemoral con­tact pressures in 12 fresh cadaver specimens. These aumors found tl1at a 1 0° increase in me Q angle resuited in a 45% increase in peak contact pressure at 20° knee flexion. In half of these specimens, tl1e area of patellar contact shifted later­ally, and the peak pressures were evident on tl1e medial portion of tl1e lateral facet.

An increased Q angle often is present with rotational malalignments of the femur and tibia. Such abnormalities include excessive femoral anteversion, lateral tibial torsion and/or lateral displacement of tl1e tibial tubercle, and genu valgum.1 ,1 0,94

Figure 18-13

Patellofemoral Joint • CHAPTER 1 8 61 1

Sagittal MRI of the knee obtained at 0° showing patella alta (left) and the normal vertical position of the

patella (right).

• Excessive femoral anteversion. In the transverse plane, the neck of the femur forms an angle of about 15° with the transverse axis of the femoral condyles (Figure 18-14). This places the femoral head anterior to the femoral

Figure 18-14 Femoral anteversion is measured by comparing the femoral neck and

posterior condylar axes in the transverse plane. Normal anteversion is

approximately 1 5° .

condyles. An increase in this angle, or excessive femoral anteversion, is associated with medial femoral rotation ( Figure 18_15).31 ,105-1 08 Excessive femoral anteversion and subsequent medial femoral rotation cause the troch­lear surface of the femur to be placed medially with respect to the tibial tubercle, functionally increasing the Q angle.lO Clinically, this is manifested by a toed-in gait and the appearance of "squinting patellae.,, ] , ] 05 Lateral tibial torsion can compensate for this deformity by straightening out the long axis of the leg; however, this also displaces the tibial tubercle more laterally, resulting in an even larger Q angle.65 Fulkerson and Hungerford3o have stated that isolated excessive femoral anteversion rarely results in patellar problems; however, femoral ante­version combined with compensatory tibial torsion increases the risk of lateral patellar displacement.

• Lateral tibial torsion and/or lateral displacement of the

tibial tubercle. A laterally displaced tibial tuberosity with respect to the midline of the tibia and the ASIS acts to increase the Q angle.iO This anatomical variation typically is the result of increased lateral tibial torsion.3o Lateral tibial torsion in subjects with PFP has not been clearly delineated and doclill1ented, which raises questions as to its clinical importance.

Trillat et al.21 and Hauser l 7 discussed the importance of the laterally displaced tibial tuberosity as a contri­buting factor in patellar malalignment. These authors described surgical procedures to correct this deformity,

61 2 C HAPTER 1 8 • Patellofemoral Joint

Figure 18-15 Excessive fcmoral anteversion i s associated with increased femoral

internal rotation. Note that this posture increases the quadriceps angle

(Q angle) .

involving transfer o f the tibial tuberosity medially to reduce the valgus forces created by an excessive Q angle. Hehne44 studied the effects of this surgery in cadaver specimens and reported that medial transfer of the tibial tuberosity resulted in a significant decrease in the total patellar contact area, especiaUy the contact area of the lateral facet. This reduction in contact area caused a 25% increase in the average patellofemoral joint stress both medially and laterally, leading the authors to dispute the effectiveness of this procedure.

• Genu valgum. Increased valgus angulation of the femur and tibia in the frontal plane is called genu valgum and is thought to be the result of a tight ITB or excessive femoral anteversion.3! Genu valgum also is postulated to increase the valgus force vector of the quadriceps mus­cle (Figure 1 8- 1 6); L O,1 09 however, this bony orientation is not consistently present in patients witl1 PFP. Soft Tissue Influences_ Both contractile and noncon­

tractile soft tissue structures can contribute to the lateral forces acting on tl1e patella. Although these effects may be present in conjunction with the abnormalities already described, their potential influence on lateral patellar track­ing must be assessed if an effective treatment is to be formulated .

Passive Structures. As mentioned previously, the lateral retinaculum has been implicated as a cause of ELPS and is

Figure 18-16 Increased angulation of thc femur and tibia in the frontal plane is

described as genu valgul11 . Note that this posture increases the Q angle.

capable of exerting a lateral force on the patella, potentially contributing to subluxation. Because the lateral retinacu­lum has an extensive attachment to the ITB, contraction of the tensor fascia lata may exert a dynamic lateral force through tllis connection. I OO In some cases this attachment has been found to be excessive, causing recurrent disloca­tion of tl1e patella. l l o Puniello 43 demonstrated a strong relationship between ITB tightness and decreased passive medial patellar glide in a group of 17 subjects with patello­femoral dysfunction. Hughston and Deese l ! I found a high incidence (50%) of medial patellar subluxation after lateral retinacular release, which indicates that tl1is structure also plays a role in pulling tl1e patella laterally. These studies support the concept tl1at a functional anatomical rela­tionship exists between the patella and the passive lateral structures of the knee.

Dynamic Structures. A force imbalance between the VM and the VL is widely accepted as a principal cause of patellar subluxation .31 ,52,1 l2-1 14 As such, clinical emphasis has been placed on the dynamic factors associated with patellar insta­bility (i.e . , VM weakness). The VM has been identified as the primary structure capable of counteracting the VL in maintaining patellar alignment. VM insufficiency has been associated with muscle atrophy, lOO, l I S hypoplasia, l oo inhi­bition caused by pain and effusion, I I 6,1 1 7 and impaired motor control. I L S

According to Fox, I00 hypoplasia of the extensor mecha­nism is found to a varying degree in 40% of the population. This hypoplasia manifests as incomplete development of the VM, because it is the last of the quadriceps muscle to develop phylogenetically. lO o The effect of an underdevel­oped VM is a patellar alignment that is influenced by an overpowering VL; more specifically, the patella is situated more laterally and proximally. The more hypoplastic the VM, the more lateral the position of the patella. In addi­tion, the superior and lateral pull of the patella can cause the development of patella alta. This hypoplasia also has been theorized to influence the development of the tibia, because the unchecked pull of the VL can result in lateral tibial rotation, lateral placement of the tibial tubercle, and genu recurvatum. 100

Fox1 00 theorized that the VM is the weakest muscle phylogenetically and therefore the first component of the quadriceps muscle to atrophy after injury or disuse. Fox considered the potential muscular imbalance between the medial and lateral dynamic stabilizers as a result of this atrophy or weakness to be the major predisposing factor for "hypermobile patella syndromes." Atrophy of the VM was observed by Smillie, I 19 who stated that the apparent wasting of the vastus medialis was associated with the inability to complete terminal knee extension. To the con­trary, Lieb and Perry54 stated that apparent atrophy of the VM was the result of a thinner fascial covering (half the thickness) compared to the VL, which made atrophy of the VL less perceptible.

Atrophy of the quadriceps muscle group is thought to be caused by reflex inhibition, I 16 with the stimulus being pain120 or effusion.121 Inhibition is the result of afferent stimuli from receptors in or around the injured knee that prevent activation of the (X-motor neurons in the anterior horn of the spinal cord.122 Spencer et al.1 16 reported that infusion of only 20 to 30 mL of saline into the knee joint exceeded the threshold for quadriceps muscle inhibition, in contrast to other authors, who have proposed much larger volumes (e.g. , 100 mL).121 In an attempt to deter­mine whether selective inhibition of the different heads of the quadriceps muscle was possible, Spencer et a1 . 11 6 exam­ined Hoffman's reflex in the individual muscles after intra­articular infusion of saline into the knee. Although the VM appeared to be affected more by small amounts of induced effusion, no statistically significant differences were seen. This finding supported previous work that showed that reflex inhibition caused by effusion affects the entire exten­sor mechanism and does not predispose the patellofemoral joint to an imbalance of dynamic forces.

Bennett and Stauberl 18 proposed a neural component of VM insufficiency. hypothesizing that underdevelopment of this muscle may result from a deficiency in motor control. These authors observed an eccentric muscle contraction deficit with isokinetic testing that demonstrated a rapid reversal with training. The quick return to normal eccentric

Patellofemoral Joint • C HAPTER 1 8 61 3

strength combined with a rapid decrease in symptoms led these researchers to conclude that these subjects had an error in the appropriate use of the VM. Exactiy how tile training of the quadriceps muscle relieved pain was not presented in this study.

It is apparent from the literature that a host of factors has been postulated to contribute to lateral patellar track­ing. Although many theories have been presented, further research is necessary to substantiate these claims.

Do patients with PFP have VMO insufficiency? Docu­menting imbalances between the VM and the VL in patients Witil PFP has been of primary interest to the practicing clini­cian, because conservative treatment of this disorder typi­caUy focuses on restoring normal function of the dynamic stabilizers.9, l o This functional imbalance is widely accepted as a cause of PFP. 1 23 Despite the interest in tile function of tile quadriceps femoris in patients with PFP, evidence sup­porting the concept of vasti muscle imbalance as a cause of lateral patellar subluxation is limited.

Because in vivo strength assessment of the individual vast us muscle is not possible, electromyography (EMG) has been used to compare the relative recruitment of these muscles, under tile rationale that decreased activity or impaired timing of the VM relative to the VL may indicate compromised medial patellar stability. Many investigators have studied the EMG activity of the dynamic patellar stabi­lizers in individuals with PFP; however, tile results of these studies are equivocal. Some studies have found signif­icant differences in VM and VL activity in patients with PFP/24- 126 whereas others have not.127-1 30 Similarly, some authors have reported that the onset of VL activity precedes tilat of VM activity in persons with PFP; 131 ,132 however, vasti tinllng differences have not been reported in all stud­ies. 133 Direct comparisons of these studies are difficult because of differences in experimental technique, methods of quantifYing EMG, and the inherent variability associated with such data.

Another reason for the inconsistent results in these investigations may be the inherent variability among patients with PFP. Because tile etiology of PFP has been considered a dynamic entity, a deficiency of tile medial sta­bilizers logically should result in lateral displacement of tile patella. However, radiological examinations have documen­ted that fewer tilan 50% of patients with PFP show isolated lateral subluxation.83,134 This suggests that lateral patellar tracking is not a universal finding in this disorder, and therefore such an inference cannot be generalized to all patients.

Etiology of Medial Patellar Subluxation. Medial subluxation of tile patella is less commonly seen than lateral patellar subluxation. The cause of lateral patellar subluxation is related more to anatomical and soft tissue abnormalities, whereas the etiology of medial subluxation is almost always iatrogenic. 95, 1 1 1 This condition most commonly is caused by excessive medialization of tile extensor mechanism in

614 CHAPTER 1 8 • Patellofemoral Joint

realignment surgery or by lateral retinacular release in which little or no patellar lateralization was done preoperatively. 30

Abnormal lower Extremity Kinematics

Researchers recently have recognized that the patellofe­moral joint can be influenced by the segmental interactions of the lower extremity.1 35 Abnormal motions of the tibia and femur in tlle transverse and frontal planes can have a substantial effect on patellofemoral joint mechanics and therefore PFP. An understanding of how the lower kinetic chain can influence the patellofemoral joint is important, because interventions to control abnormal lower extremity mechanics are not focused on tlle area of pain, but ratller on the joints proximal and distal to tlle patellofemoral joint (i.e., tlle hip and/or foot and ankle) . As noted previously, structural deformities can lead to an increase in the Q angle and the lateral forces acting on the patella; however, abnor­mal motions of the lower extremity also can be contributing factors. 135 Three principal lower limb motions can influence the dynamic Q angle: tibial rotation, femoral rotation, and knee valgus.

Tibial Rotation The Q angle can be influenced distally through motions of the tibia. Lateral rotation of the tibia moves tlle tibial tuberosity laterally, tllereby increasing the Q angle, whereas tibial medial rotation decreases the Q angle by moving the tibial tuberosity medially (Figure 1 8- 1 7, A). In turn, tibial rotation is influenced by subtalar joint motion. Subtalar Jomt pronation causes medial rotation of the tibia, and supination causes the tibia to rotate laterally. Normal

B Figure 18-17

subtalar joint pronation occurs during the first 30% of the gait cycle, during which tlle tibia rotates medially 6° to 10° .1 36 This motion occurs in response to the medial rota­tion of tlle talus as it falls into the space created by the inferior and lateral movement of the anterior portion of the calcaneus.

As a result of tlus close biomechanical relationship between the rearfoot and the tibia, abnormal pronation has been linked to several lower extremity conditions, including patellofemoral joint dysfunction. Typically, pro­nation is considered abnormal if the anlount of motion is excessive or occurs at tlle wrong time (i.e., when the foot should be supinating). When excessive pronation is related to various clinical entities, an assumption is made that abnormal pronation results in excessive tibial medial rota­tion and that this motion places a rotatory strain on soft tissues of the lower extremity. Although tllis may be tlle case with respect to tlle tibiofemoral joint, the same assumption does not hold true for the vertically aligned patellofemoral joint. In fact, excessive tibial medial rotation caused by subtalar joint pronation would actually decrease

the Q angle and tlle lateral forces acting on the patella (see Figure 1 8 - 1 7, A).

This discrepancy was noted by Tiberio,137 who described a scenario in which excessive pronation could affect normal patellofemoral joint function. Tiberio postu­lated that to achieve knee extension in midstance, the tibia must rotate laterally relative to the femur to ensure ade­quate motion for the screw home mechanism. To compen­sate for this lack of tibial lateral rotation because of the failure of tlle foot to resupinate, the femur would have to rotate medially on the tibia such that the tibia was in

c

Schematic of the influence of femoral and tibial motion on the Q angle. A, Tibial internal rotation results in a dccrease in the dynamic Q angle. B, Femoral internal rotation increases the dynamic Q angle.

C, Fcmoral adduction and/or tibial abduction results in knee valgus and an increase in the dynamic

Q angle. (From Powers CM: The influence of altered lower-extremity kinematics on patellofemoral joint dysfunction: a theoretical perspective, ] Orthop Sports Phys Ther 33:639-646, 2003.)

relative lateral rotation. This compensatory medial rotation of the femur would permit the necessary screw home mechanics to allow for knee extension. However, excessive medial rotation of the femur would move the patella medi­ally with respect to the ASIS, thereby increasing the Q

angle and the lateral component of the quadriceps muscle vector (Figure 1 8- 1 7, B). This would appear to be a plausi­ble biomechanical means by which pronation could influ­ence the patellofemoral joint; however, to do so, such motion ultimately would have to influence the femur.

An assumption made in the scenario just described is that if excessive pronation is evident in midstance, then excessive medial rotation of the tibia also should be evident. However, a recent study by Reischl et al . 1 36 reported that the magnitude of foot pronation did not predict the magni­tude of tibial or femoral rotation . Also, the magnitude of tibial rotation did not predict the magnitude of femoral rotation, which indicates that excessive rotation of the tibia did not translate into excessive femoral rotation. This is not surprising, considering that the knee has the potential to absorb rotatory forces through its transverse plane motion. It should be noted that all subjects in this study demon­strated pronation and tibial medial rotation during early stance . However, this motion was not a 1 : 1 ratio. Individ­ual factors, such as the orientation of the subtalar joint axis and the amount of transverse plane motion between the rear foot and the lower leg, likely influence the degree to which pronation can influence the magnitude of tibial rotation.

Femoral Rotation The Q angle can be influenced proximally through motions of the femur. As described previously, increased femoral medial rotation results in a larger Q angle, because the patella is moved medially with respect to the ASIS (see Figure 1 8- 1 7, B). Consequently, femoral lateral rotation minimizes the Q angle, because the resultant line of action of the extensor mechanism is more in line with the ASIS.

Apart from increasing the Q angle and the laterally djrected forces on the patella, femoral medjal rotation can influence patellar alignment and track.jng. Because the patella is tethered in the quadriceps tendon, it is not obli­gated to follow the motions of the femur (i.e., trochlear groove), especially when tlle quadriceps muscles are con­tracted. In fact, during weight-bearing activities, medial rotation of the femur can occur independent of patellar motion, thereby bringing tlle lateral anterior femoral con­dyle in close approximation to the lateral facet of the patella. Using dynamic MRI methods under weight-bearing conditions (a single-leg partial squat), Powers et al.l 38 demonstrated that the primary contributor to lateral patellar tilt in a group of individuals with patellar instability was femoral motion (medial rotation), not patellar motion (Figure 1 8 - 1 8 ) . Tlus finding calls into question the long­held assumption that subluxation is the result of the patella

Figure 18-18

Patellofemoral Joint • CHAPTER 1 8 61 5

Influence of femoral rotation on lateral patellar tilt at 0° knee flexion. During the non-weight-bearing condition (A), lateral patellar tilt was the result of patellar rotation (ex) on a relatively horizontal femur (9) .

During the weight-bearing condition (B), lateral patellar tilt was a result of internal rotation of the femur (9) under a relatively horizontal

patella (ex) . ( From Powers eM, Ward SR, Fredericson M et al :

Patellofemoral kinematics during weight-bearing and non-weight­bearing knee extension in persons with lateral subluxation of the

patella: a preliminary study, ] Orthop Sports Phys Ther 33:677-685,

2003. )

moving on the femur. Although this may be the case during non-weight-bearing activities in which the femur is fixed (i .e . , during knee extension in sitting), this study provides evidence that lateral subluxation of the patella during weight-bearing activities may be the result of the femur rotat­ing underneath tlle patella.

As described previously, excessive medial rotation of the femur during midstance may be a compensatory mecha­nism to ensure normal knee screw home mechanics in tlle presence of abnormal pronation and excessive tibial medial rotation. However, motion of the femur also can be influ­enced proximally. The hip joint offers a great deal of mobil­ity and depends on adequate muscular control for stability. Clinically, weakness of the hip lateral rotators (i.e . , gluteus maximus and deep rotators) can result in a "rolling in" of the tlUgh during early stance and may have a deleterious effect on the patellofemoral joint. In addition, as described previously, excessive femoral anteversion biases tlle lower

616 CHAPTER 1 8 • Patellofemoral Joint

extremity into medial rotation and can result in the clinical appearance of "squinting patellae," a toed-in gait, or both. I , I OS

Knee Valgus Apart from abnormal motions in the transverse plane, excessive frontal plane motions can influence the patellofe­moral joint. Most notably, valgus at the knee increases the Q angle, because the patella is displaced medially with respect to the ASIS (Figure l S- 1 7, C) . In comparison, a varus position of the knee decreases the Q angle, because the patella is brought more in line with the ASIS.

Knee valgus can be the result of thigh adduction, tibial abduction, or a combination of these two (see Figure lS -1 7, C) . Excessive femoral adduction during dynamic tasks can be the result of weakness of the hip adductors, particu­larly the gluteus medius. The upper fibers of the gluteus maximus and the tensor fascia lata also assist in abduction at the hip and, if weak, may contribute to excessive thigh adduction.1 39 Structural abnormalities of the femur (i.e., excessive anteversion and coxa valga) can reduce the moment arm of the gluteus medius, which may result in a fimctional weakness. Tibial abduction can be the result of excessive pronation or frontal plane motion at the ankle. However, it should be noted that tibial abduction also could be an accommodation to femoral adduction, because the proximal tibia is obligated to follow the distal femur. Ireland et al. 140 provided evidence supporting the premise that proximal hip weakness may contribute to altered lower extremity motions in individuals with PFP. They reported that these individuals had 26% less hip abductor strength and 36% less hip external rotator strength than pain-free controls.

Overuse

Because only 50% of patients with PFP have tracking abnormalities, other factors must be involved. If patellofe­moral joint function and gait mechanics are normal, patel­lofemoral joint pathology may be related to excessive activity levels, or overuse. For example, the peak PFJRF during weight acceptance has been calculated as 7 to 1 1 times body weight for healthy runners, a value estimated to be near the physiological limit of involved tissues.80 Therefore, for a given knee flexion angle, high forces result in elevated patellofemoral joint stress and may be problem­atic because of the repetitive nature of such activity. This concept is supported by the work of Thomee et al., 1 41 who studied 40 women with PFP and concluded that chronic overloading and temporary overuse were the primary causes of symptoms.

Overuse injuries are a fill1ction of the magnitude of the applied force and the number of cycles the load is applied. For example, as the load increases, the number of repeti­tions necessary to cause injury decreases. Conversely, as

the load decreases, the number of repetitions necessary to cause injury increases. Activities commonly associated with overuse histories include long distance running and cycling. 142

Summary

Figure l S - 19 summarizes the potential factors that may lead to pateLlofemoral joint dysfunction and pain. To treat PFP effectively, the clinician must address the root causes of the pain and dysfimction. Therefore the goal of the examination is to identify the likely cause or causes of symptoms so that the most effective interventions can be applied.

Examination

The goal of the examination is to obtain pertinent data to allow the formulation of a hypothesis about the cause of the symptoms. The examination should include both subjective and objective physical components.

Subjective Examination

The subjective examination is essential for making an accu­rate diagnosis. When taking a patient's history, the clinician should determine what problems are important and what types of examinations may be useful . Key information to obtain includes the patient's current complaints, symptoms, and the mechanism of injury.

Patients typically report pain as diffuse and arising from the anterior aspect of the knee. 140 However, sharp, "stab­bing" symptoms can be elicited with provocative testing. Pain often is induced by activity and aggravated with filI1c­tions that increase patellofemoral compressive forces, such as ascending and descending stairs, inclined walking, squat­ting, and prolonged sitting. I ,90 The sensation of "giving way" also may be reported and should be differentiated from tibiofemoral joint instability (i.e., ligament tear) or quadriceps muscle inhibition.

Pain along the medial and lateral borders of the patella is a common complaint, and retropatellar and inferior pain often is reported. Patients frequently report crepitus with knee flexion, but this should not by itself cause con­cern, because asymptomatic patellofemoral crepitus is very common.143 Painful crepitus may be related to tightness of the deep retinacular tissues, plicae, or patellofemoral joint instability; it is not necessarily suggestive of arthritic changes.

According to Grelsamer and McConnell/2 the location of symptoms may indicate the specific structures involved and provide direction with respect to a differential dia­gnosis:

• Lateral: Small nerve injury of the lateral retinaculum • Medial: Recurrent stretching of the medial retinacu­

lum/medial patellofemoral ligament

Patellofemoral Joint • C HA PTER 1 8 61 7

Altered PFJ Mechanics Altered Lower Extremity Mechanics Overuse

Soft Tissue Muscular Bony Structural Imbalances Deformities

Altered PFJ Kinematics and I or Alignment

j J,Patellofemoral Contact Area

Transverse Plane Deviations

Femoral and Tibial Rotation

1 Increased Dynamic a-Angle

1 Altered PDJ Kinematics and I or Alignment

1 J,Pateliofemoral Contact Area

j

Frontal Plane Deviations

Knee Valgus

1 Increased Dynamic a-Angle

1 iLateral PDJ Compression

1

Sagittal Plane Deviations

Excessive Inadequate

T'-r iauad Force J,Pateliofemoral 1 "'�" ' ..

iPateliofemoral Joint Reaction Force

iLoading Cycles

iLoading Magnitude

\ / iPateliofemoral Joint

Reaction Forces

j Patel iofemoral Joint Stress

Patellofemoral Pain and/of Pathology

Figure 18-19 Flow diagram of potential mechanisms of patcllofemoral pain and/or pathology.

• Retropatellar: Articular cartilage damage; stress borne on subchondral bone

• Su,perior: Quadriceps tendonitis/tendinosis • Inferior: Patellar tendonitis/tendinosis; fat pad

irritation Throughout the history process, it is important to ascer­

tain whether the patient's disability is related to pain or instability. Generally speaking, the onset of PFP is insidious and progression is slow. A specific episode or event is not always reported. However, the cliniciaJl should pay careful attention to the patient's perceived cause of the injury, making note of changes in lifestyle, activity levels and, with athletes, training habits. A slow onset of symptoms may indicate an underlying biomechanical error or structural faults that manifest themselves over time. A rapid onset of symptoms may be associated with overuse and may or may not have an underlying biomechanical cause.

Histories related to traumatic injury (i.e., direct falls on the patella) or instability related to pain are fairly obvious and self-explanatory. However, biomechanical abnormal­ities or structural faults may have been present before the injury (e.g., pronation, excessive femoral anteversion), and these factors may be responsible for the perpetuation of symptoms.

Physical Examination

The physical examination should include ( 1 ) testing proce­dures necessary to make a differential diagnosis; (2) evalua­tion of the patellofemoral joint, inclucling alignment, mobility, and dynamic motion; and ( 3 ) assessment of lower extremity alignment and function.

Differential Diagnosis To diagnose PFP accurately, the clinician must rule out other structures as potential sources of anterior knee pain symptoms.

Patellar Tendonitis/Tendinosis. The symptoms of patellar tendonitis/tenclinosis can be very similar to those of PFP, because pain is often induced by activity, especially during high speed eccentric contractions of the quadriceps muscle. A clear clistinction CaJl be made between tendon­itis/tendinosis and PFP through careful palpation. Local tenderness to the quadriceps tendon (superior to the patella) aJld patellar tendon (inferior to the patella) indi­cates tendonitis/tenclinosis and should not be confused with retropatellar pain or medial or lateral patellar pain.

Iliotibial Band Friction Syndrome. ITB friction syndrome is characterized by localized pain in the lateral

61 8 C HAPTER 1 8 • Patellofemoral Joint

aspect of the knee (lateral epicondyle of the femur). Occa­sionally crepitus or "snapping" can be palpated as the ITB crosses the lateral femoral condyle (approximately 30° flex­ion). Occasionally this is mistaken for patellofemoral joint crepitus.

Meniscal and Ligamentous Structures. Structures of the tibiofemoral joint should be ruled out as possible causes of symptoms. Meniscal tests, such as joint line ten­derness, McMurray's test, Apley's compression test, and the Bounce home test, should be performed to rule out internal derangement. 1 44 Likewise, ligamentous tests should be performed (i.e., Lachman's test, varus and valgus stress tests), especially in patients with traumatic histories and/or acute swelling.

Referred Pain. Referred pain from compression and/ or irritation of the L3 or L4 nerve roots can manifest itself as vague pain along the lateral border of the thigh. Patients should be carefully screened to rule out lumbar spine pathology.

Evaluation of the Patellofemoral Joint The examiner should observe for redness, swelling, warmth, dystrophic changes, or obvious joint deformity. In addition, the presence of quadriceps muscle atrophy should be determined (either qualitatively or quantitatively with a tape measure). With athletes, quadriceps muscle atrophy may not be present.

Selective atrophy of the VMO in relation to the rest of the vasti has never been documented in patients with PFP, and evidence suggests that atrophy of the quadriceps mus­cle affects all of the vasti equally.145 Because the VMO is the most visible of the vasti (as a result of its superficial fibers and thin retinacular covering), atrophy is more appar­ent in d1is muscle. Atrophy of dle VL is much more diffi­cult to visualize, because most of its fibers are deep and wrap around to the posterior femur; for this reason, the cli­nician must be cautious about attributing PFP symptoms solely to VMO atrophy.

Tests for Effusion. Because quadriceps muscle inhibi­tion is associated with slight swelling, general observations about effusion should be made (e.g., joint warmdl, red­ness). Typically, PFP of a nontraumatic nature is associated with only mild effusion. Severe effusion likely indicates a more serious ligamentous injury. Major effusion can be assessed by compressing dle patella into the trochlea. A positive ballotable patella sign is seen when the patella quickly "rebounds" or "floats" when compressed into the trochlea.144

Minimal joint effusion can be assessed with the knee extended by "milking" fluid from d1e suprapatellar pouch and the lateral side of d1e knee into the medial side of dle knee. A small bulge medially is a positive sign of mild swelling. 1 44

Patellar Alignment. The patella should be assessed for gross alignment abnormalities. Typically dlis is done

with the patient supine, the knee extended, and the quadri­ceps muscle relaxed. The assessment criteria established by McConnelf have been used extensively in clinical practice. The most commonly observed abnormalities in individuals widl PFP are as follows:

McConnell's Assessment Criteria for Patellar Alignment

• Lateral glide (displacement)

• Lateral tilt

• Lateral rotation

• Inferior tilt

• Lateral glide (displacement) . The distance from the medial epicondyle of d1e femur to the center of the patella is greater than d1C distance from the lateral epicondyle of d1e femur to the center of the patella (Figure 1 8-20) .

• Lateral tilt. The lateral border of the patella i s lower d1an dle medial border (as viewed in dle transverse plane; Figure 18-2 1 ) .

• Lateral rotation. The inferior pole of the patella is rotated externally with respect to the midline of d1e d1igh (as viewed in the frontal plane; Figure 1 8-22 ) .

• Inferior tilt. The inferior pole of the patella is tilted posteriorly compared to d1e superior pole (sagittal plane; Figure 18-2 3 ) .

Ideal alignment

Figure 18-20

Lateral glide of the patella

Assessment of the glide component. Ideally the patella should be centered on the superior portion of the femoral articular surface. (From

McConnell J, Fulkerson J: The knee: patellofemoral and soft tissue

injuries. In Zachazewski JE, Magee DJ , Quillen WS, editors: Athletic

i�ljttries alld rehabilitation, p 7 I l , Philadelphia, 1 996, WB Saunders . )

Ideal alignment

Figure 18-21

Lateral tilt of the patella

Assessment of tl�c tilt component. Ideally the patella should be parallel

to the fTontal plane of the knee. (From McConnell J, Fulkerson J: The

knee: patellofemoral and soft tissue injuries. In Zachazewski JE, Magee

DJ, Quillen WS, editors: Athletic injuries and rehabilitation, p 7 1 2,

Philadelphia, 1 996, WE Saunders . )

Ideal alignment

Figure 18-22

External rotation

Assessment of the rotation component. Ideally the superior and

inferior poles of the patella should be in line with the long axis of the femur. (From McConnell J , Fllikerson J : The knee: pateUofemoral and

soft tissue injuries. In Zachazewski JE, Magee DJ, Quillen WS, editors:

Athletic inittries and rehabilitation, p 7 1 2, Philadelphia, 1 996, WE Saunders . )

Patellofemoral Joint • C H APTER 1 8 61 9

Ideal alignment

Figure 18-23

Posterior tilt of the inferior pole

Assessment of the flexion component. Ideally the superior and inferior

poles of the patella should be in line with the long axis of the femur.

Excessive inferior tilt of tl,e patella may irritate the infrapatcllar fat pad. (From McConnell J, Fulkerson J: The knee: patellofemoral and soft

tissue injuries. In Zachazewski JE, Magee DJ, Quillen WS, editors:

Athletic injuries and rehabilitation, p 7 1 2, Philadelphia, 1 996,

WE Saunders.)

Although this classification system is widely used, both the validity and reliability of these techniques in assessing patellar alignment have been challenged. 1 46, 1 47 Care must be taken in the interpretation of the results of patellar align­ment testing, especially because the resting position of the patella tends to be one of sLight lateral displacement and lateral tilt. Only obvious abnormalities should be considered relevant.

Passive Patellar Mobility. In addition to static align­ment, passive patellar mobility should be evaluated. Because motion of the patella is necessary for normal joint function, assessment of patellar mobility is an important component of the examination. The patella should be able to freely glide superiorly and inferiorly, as well as medially and laterally. Also, the clinician should be able to tilt the patella medially to raise the lateral border. Quite often patellar mobility is restricted after prolonged immobilization or surgery. Tight­ness of the lateral retinaculum is the most common limiting factor and manifests as decreased medial patellar glide and inability to tilt the patella medially. As the patella moves inferiorly and superiorly and the knee flexes and extends, adequate motion is essential to ensure normal knee motion.

When assessing passive patellar mobility, the clinician also should note excessive translations and/or apprehension to such movements. Excessive lateral translation of the patella may indicate tearing of the medial patellofemoral Ligament. Patient apprehension to a lateral glide of the patella suggests recurrent patellar dislocation

Patellar Tracking. Active patellar tracking is best observed with the patient in the sitting position . The

620 C HAPTER 1 8 • PatelJofemoral Joint

patient should be asked to extend the knee slowly while the clinician observes the motion of the patella. As mentioned previously, normal motion is characterized by slight medial motion as the knee extends from 45° to 1 8° , followed by slight lateral motion in terminal knee extension. Patellar subluxation typically occurs during terminal knee exten­sion, therefore particular attention should be focused on this part of the range. As with static patellar alignment, only large deviations should be considered significant. Clinicians must keep in mind that subtle subluxations are very diffi­cult to pick up, because a large "grey zone" exists between normal and abnormal.

The clinician also should be aware of any painful arc of motion and should note tlle range in which pain is repro­duced. Pain typically is more evident during the last 20°, because greater quadriceps muscle forces are necessary to complete terminal knee extension, and the patellofemoral joint contact area decreases ( resulting in elevated patellofe­moral joint stress) .

As tlle knee i s extending, tlle examiner should make a qualitative assessment of tlle state of quadriceps muscle contraction. Does tlle knee appear to have difficulty com­pleting terminal extension (which suggests quadriceps mus­cle weakness), or is muscle "quivering" present (suggestive of reflex inhibition)?

Quadriceps Muscle Weakness. General quadriceps muscle weakness or atrophy (or both ) is a hallmark of PFP. However, ascertaining whether true weakness is pres­ent is difficult, because pain commonly is reproduced with quadriceps muscle contraction and tlle patient may be hesi­tant to give a maximum effort, thereby invalidating results.

Tests for Soft Tissue and Muscle Tightness. Tightness of various soft tissues and muscles that cross the knee can have an adverse effect on patellofemoral joint function. In particular, tightness of tlle rectus femoris, ten­sor fascia lata/iliotibial band complex, and the hamstrings should be addressed.

Tightness of the rectus femoris can result in excessive patellofemoral joint compression, especially when the knee is flexed and the hip is extended. This posture is particularly evident during the swing phase of the running cycle. The length of the rectus femoris is best assessed using Thomas's test. 1 48 With the patient supine, both knees are brought to tlle chest to flatten tlle lumbar lordosis. The leg being tested then is allowed to extend such that it comes to rest on the table in a neutral position. If the knee cannot flex to 90° witll the hip in a neutral position, the rectus femoris is considered tight.

As noted previously, tlle interdigitation of the ITB and tlle lateral retinaculum suggests that tightness of this struc­ture may produce a lateral force on tlle patella, potentially contributing to lateral subluxation and ELPS. Ober's test assesses for tightness of the ITB and tensor fascia lata. For tllLS test, tlle patient is placed in the side lying position. The examiner passively abducts and extends the patient's

upper leg with tlle knee straight or flexed to 90° . The examiner then slowly lowers the thigh. 148 If tightness or contracture is present, tlle leg remains abducted and does not come to the neutral position.

The hamstrings do not cross the patellofemoral joint, tllerefore these muscles do not have a direct influence on tllat joint. The hamstrings should be considered only as being contributory to PFP if tightness results in an abnormal walking or running pattern. For example, hamstring tight­ness may lead to excessive knee flexion during tlle stance phase of walking or running. Excessive knee flexion requires quadriceps action to support this posture, resulting in elevated patellofemoral joint forces. Hamstring length is assessed using tlle straight leg raise test. 1 48 For normal ham­string function, 70° to 80° hip flexion should be achieved Witll the knee extended and the lumbar spine flattened.

Assessment of Lower Extremity Alignment and Function As noted previously, recent evidence suggests that patellofe­moral pain and dysfunction may be related to abnormal lower extremity mechanics. For this reason, carefid assess­ment of lower extremity alignment and dynamic fill1ction is an important aspect of the physical examination.

Standing Posture. The patient should be observed during relaxed standing. The examiner also should observe the alignment of the knee in the sagittal and frontal planes, as well as the transverse plane alignment of the lower extremity.

Sagittal Plane Alignment of the Knee. The knee should be evaluated for hyperextension or excessive knee flexion. Knee hyperextension (genu recurvatum) may result in compression of tlle inferior pole of the patella into the

infrapatellar fat pad . A hyperextended knee also may indi­cate quadriceps muscle weakness or inhibition, because tlle patient may rely on the posterior capsule for stability ratller than active quadriceps muscle contraction.

Excessive knee flexion ( i .e . , inabi lity to extend the knee fillly) requires greater amounts of quadriceps contraction to maintain this posture. In turn, the quadriceps contrac­tion increases the compressive forces acting on the patello­femoral joint. Excessive knee flexion may be related to loss of terminal knee extension after surgery (particularly ante­rior cruciate ligament [ACL] reconstruction), hamstring tightness, hip flexion contracture, or a weak calfl 39

Frontal Plane Alignment of the Knee. Some have suggested that valgus and varus alignment of the knee is related to the structure of the proximal femur. For example, the normal inclination between the femoral neck and the femoral shaft is 1 25° . 1 49 A reduction of this angle ( i . e . , coxa vara) results in a valgus orientation of the knee. An increase in the angle of inclination results in a varus orientation of tlle knee . Knee valgus tends to increase the Q angle and tlle lateral forces acting on the patella, whereas knee varus has the opposite effect. However, coxa valga

reduces the lever arm of the gluteus medius, thereby reduc­ing the torque-producing capacity of this muscle . I SO

Transverse Plane Alignment of the Lower Extremity. Medial rotation of the femur (medial femoral torsion ) results in "squinting patellae," whereas lateral rota­tion of the femur (lateral femoral torsion) results in the patella pointing outward ( i .e . , "grasshopper eyes" ) . (NOTE: Torsion implies acntal anatomical rotation of the femur, not the physiological movement of the femur. ) Femoral medial rotation may indicate excessive femoral anteversion or fem­oral torsion, whereas femoral lateral rotation may suggest femoral retroversion or lateral femoral torsion. Careful attention must be paid to whether foot pronation is evident, and whether the entire lower extremity is in a posture of medial rotation or whether the medially rotated position of the femur appears to be an isolated entity.

Dynamic Function. Perhaps one of the most impor­tant aspects of the examination is observation of dynamic movement. This should include analysis of level walking, as well as higher demand activities, such as running, ascend­ing and descending stairs, squatting, and jumping. Careful attention should be paid so as to identifY movement pat­terns that increase quadriceps demand and/or increase the dynamic Q angle. Observations also should be made with respect to the speed of ambulation, the force of impact dur­ing loading response, and any reproduction of symptoms. Components of the dynamic evaluation should be used to confirm or refute suspected abnormalities based on static testing procedures. Movements should be observed from both the frontal and sagittal views.

Sagittal View. The primary deviations for which the examiner should watch in the sagittal plane are inadequate

Figure 18-24

Patellofemoral Joint • C HAPTER 1 8 621

knee flexion or hyperextension during weight acceptance and excessive knee flexion during stance. Decreased knee flexion during weight acceptance and knee hyperextension during the stance phase may indicate a quadriceps avoidance gait pattern caused by weakness or pain . The functional significance of inadequate knee flexion during weight accep­tance is that shock absorption is impaired, and the tibiofe­moral joint may be sllsceptible to excessive impulse loading. In addition, decreased knee flexion reduces the contact area between the patella and femur and therefore may contribute to elevated joint stress.

Excessive knee flexion increases pateUofemoral joint reaction forces, because the quadriceps are overly active to support the flexed knee posture. As noted previously, causes of excessive knee flexion include knee flexion contracture, hamstring tightness or spasticity, hip flexion contracture, and weak calf muscles. 1 39

Frontal View. In the frontal view, rotation and valgus of the lower extremity are particularly important. An attempt should be made to evaluate for the following abnormalities:

1 . Does the patient pronate excessively? If so, does this result in excessive medial rotation of the tibia and femur?

2. Does the patient show excessive medial rotation of the femur? If so, does this medial rotation tend to be present throughout the gait cycle (suggesting a fixed, bony deformity, such as excessive femoral ante­version) or does the patient "collapse" into medial rotation during weight acceptance? The latter is more indicative of poor muscular control or wea.kness of the hip lateral rotators (Figure 1 8 -24) .

Frontal plane observational gait analysis o f a n individual with pateUofemoral pain. Note the collapse into

femoral internal rotation in midstance. Markers placed on the distal thigh, patella, and tibial tuberosity aid

visualization of segment motions.

622 C HAPTER 1 8 • Patellofemoral Joint

3 . Does the patient show excessive adduction of the femur

and/or a contralateral pelvic drop? This indicates poor muscular control of the hip abductors. In many instances, frontal and transverse plane abnorm­

alities are not readily evident during walking; therefore higher demand or functional activities specific to the patient need to be assessed. The repetitive step-down test is useful in this respect. The patient stands on a 0 .2 m (8-inch ) step and then lowers himself or herself with the pain­ful leg and touches the heel to the floor ( Figure 1 8-25 ) . This i s repeated 1 0 times without stopping.

In general, an attempt should be made to determine whether frontal and transverse plane deviations are occur­ring from the foot upward or from the pelvis downward. If the primary cause of the abnormality is identified, the correct treatment can be applied ( i .e . , proximal control through the hip versus distal control through the foot) .

Additional Tests. Depending on the findings of the assessment of lower extremity alignment and dynan1ic function, the clinician may require additional informa­tion to formulate a hypothesis about the cause of the pos­ture or motion abnormalities. The following tests may be usefu l : • Manual muscle test of the hip lateral rotators and hip

extensors. If excessive dynamic medial rotation and/or adduction of the femur is observed during the dynamic assessment and muscle weakness is suspected, manual muscle testing of the hip abductors, lateral rotators, and extensors is warranted.

Figure 18-25

• Assessment of hip range of motion. Hip range of motion should be evaluated because restricted lateral rotation range of motion can bias a patient into a medial rotation position. Tightness of the hip flexors also can create an medial rotation bias . Hip flexor tightness can be assessed using Thomas's test, as described previously.

• Craig)s test of femoral anteversion. Excessive femoral anteversion can result in medjal rotation of the femur and can have a significant influence on the patellofemoral joint. Crajg's test is performed with the patient prone and the knee flexed to 90° . The examiner palpates the posterior aspect of the greater trochanter of the femur, and the hip then is passively rotated medially and laterally until the greater trochanter reaches its most lateral posi­tion ( Figure 1 8 -26) . The degrees of anteversion can be estimated based on the angle of the lower leg with the vertical. Normal femoral anteversion is 1 5° .

• Foot evaluation. I f subtalar joint pronation i s identified as a potential contributor to faulty lower extremjty mechanics, the foot should be examined closely for fixed, bony defor­mities ( i .e . , rearfoot varus, forefoot varus) , muscle tight­ness ( i .e . , gastrocnemius and soleus), and weakness of dynamic stabilizers ( i .e . , tibialis posterior and peroneals).

Diagnostic Imaging

Different diagnostic imaging procedures have been sug­gested to further aid the diagnosis and management of patellofemoral pajn . However, the wide variability in the

Assessment of lower extremity dynamic control. The patient slowly lowers herself with the extremity of

interest and touches the heel to the floor without transferring weight to the descending l imb. This patient

shows medial collapse of the knee (excessive femoral adduction and internal rotation ) .

Figure 18-26 Craig's test of femoral anteversion. The examiner palpates the greater

trochanter of the femur and rotates the femur internally and externally until the greater trochanter is at its most laterally prominent position.

The angle of anteversion is estimated by measuring the angle created by the tibial shaft and a vertical line. Normal femoral anteversion is

approximately ] 5° .

radiographic findings of patients with patellofemoral dys­function, as well as the difficulty involved in demonstrating radiographic abnormalities consistent with clinical findings, has contributed to confusion in the diagnosis and classifica­tion of patients with patellofemoral pain disorders. 85 , 1 5 1 , 1 52

Despite this, numerous authors have reported that mal­position can be accurately and reliably evaluated radio­graphically using certain techniques.85, 1 53- 1 S7 One of the main disadvantages of radiographic examination is that the patient's knee usually is x-rayed when it is not weight bearing, with the quadriceps muscle relaxed; therefore the dynamic properties of patellar tracking are not considered.

Overall, few studies have used radiographic measure­ment of alignment as an evaluation for surgical or conserva­tive treatment. Insall et al . 1 S8 found that, after a proximal surgical realignment of the tibial tubercle, 52 of 57 subjects had congruence angles ( i .e . , a measure of patellar alignment in the trochlear groove) that were considered normal . Unfortunately, few preoperative measures were available for comparison. Moller et al . l S9 investigated patellar align­ment in three groups (normal subjects, recurrent subluxers, and those with anterior knee pain) by measuring the con­gruence angle with and without the quadriceps contracted, before and after 3 mon ths of isometric quadriceps exercises. The congruence angle during a maximum quadriceps con­traction became less positive for the recurrent subluxers after the exercise program. It did not change in the other groups. Fulkerson et al .9 1 used computed tomography (CT) to assess patellofemoral alignment before and after surgical lateral release. The congruence angle and lateral patellofemoral angle were determined at 0° , 1 0° , 20°, and

Patellofemoral Joint • C HAPTER 1 8 623

30° preoperatively and postoperatively. The results demon­strated that lateral release significantly reduced abnormal patellar tilting. Reigler1 60 had similar results in assessing the outcome of this surgery.

A study by Ingersoll and Knight l 6 1 demonstrated tllat 3 weeks of biofeedback training to the VMO produced a sig­nificant decrease (p <0.05 ) in the radiographic measurement of tlle congruence angle, but 3 weeks of general quadriceps strengthening had no effect on tlle congruence angle.

Robertsl62 investigated the effect of patellofemoral tap­ing on lateral patellar displacement, the lateral patellofemoral angle, and the congruence angle. The subjects were radio­graphed in the standing position witll the knee flexed to 30° . These researchers found mat, even though tlle changes were small, tlle patellofemoral angle and lateral patellar dis­placement improved significantly with taping (p = 0.0003 and 0.0002, respectively). The changes in the congruence angle were not significant. Bockratll et al . 1 63 also fowld no significant change in me congruence angle witll taping, but they found that patellar taping significantly reduced per­ceived pain levels during a 0.2-m (8-inch) stepdown test. They concluded that the reduction in pain was not asso­ciated with patellar position changes. McConnell l64 found that when subjects performed maximum isometric con­tractions between 20° and 70° while a lateral view of tlle patellofemoral joint was dynamically imaged witll video fluo­roscopy, a change occurred in the patellofemoral contact point (defined as tlle midpoint of the contact area) such tllat when tlle patella was taped, the contact area was more distal than when the patella was not taped. A corresponding increase in muscle torque was also found when tlle patella was taped. The reason for this has not yet been established, but pain relief may well account for the improved function.

Basic Radiographic Methods

The anteroposterior (AP) view is used to evaluate the patella for any fracture or bipartite configuration and for gross positional changes, such as dislocation or abnormal­ities of patellar height. Asymmetry of the femoral condyles may indicate abnormal femoral torsion or femoral neck anteversion. l S 1 A 30° knee flexion, weight-bearing, poster­oanterior ( PA) view is most important for evaluating joint space and assessing for evidence of osteoarthritis.

Radiographs for Patellofemoral Pain

• AP view in extension • AP view in 30° flexion

• Lateral view in full extension

• Lateral view in 30° flexion

• Axial view in 45° flexion

• Tangential view

624 C HAPTER 1 8 • Patellofemoral Joint

The lateral view in full extension and at 30° knee flexion is used to determine patellar height and the patella's rela­tionship to the trochlea. At full extension the lateral view should show the distal articular surface of the patella just at the center of the trochlea. J 65 Other authors have pro­posed reliable methods for assessment of patella alta and patella baja.99, 1 66

The patellofemoral joint also is visualized on an axial or tangential view. The axial view describes the parallel rela­tionship of the x-ray beam with respect to the axis of the anterior tibia, whereas the tangential view describes the per­pendicular relationship of the x-ray beam to the joint sur­faces. 1 54 Both of these methods provide cross sectional information about the relationship of the patella to the trochlear groove. l S I Overall, the most useful axial radio­graph is the simple 30° or 45° knee flexion axial view. It is most important to ensure an accurate, reproducible 30° or 45° flexion. A wooden leg holder with pins at the desired flexion angle is helpful. The authors of this chapter recommend obtaining this view, in a standardized fashion, on all patients.

A variety of methods and techniques have been described since the first tangential view was developed by Settegast in 1 92 1 . A number of modifications have been proposed, mainly in the variation of the knee flexion angle and the angle of the x-ray beam. For reproducible tangen­tial views, certain requirements must be met. The x-ray beam and x-ray plate must be perpendicular to prevent distortion. 1 54, 1 67 Views with the knee flexed more than 45° are used I 5 1 , 1 54, 1 68 but are much less helpful . The position of potential maximum instability is 0° to 30° ,

but this position is technically difficult to capture on an axial radiograph. 1 69, 1 70 For the most reliable and repro­ducible results, 45° seems to be the preferred position . 1 56

Some authors contend that tangential projections throughout the range ( i . e . , 30°, 60°, and 90° ) are vital to the assessment of dynamic tracking of the patella. 1 69, 1 70

However, in the authors' experience, this does not seem worthwhile.

Computed Tomography

CT offers the advantage of a specific, definable plane. In general, CT is best performed using a mid patellar trans­verse image, including the posterior condyles of the femur. This view enables the clinician to wlderstand the relation­ship of the articulating midportion of the patella with its reciprocal portion of the trochlea at any degree of knee flexion . Midpatellar transverse images through the poste­rior condyles with the knee flexed at 0°, 1 5° , 30°, and 45° provide an excellent depiction of how the patella enters the trochlea during flexion ( Figure 1 8 -27) . The images may be taken with the quadriceps contracted and with it relaxed. On CT, the patella should be centered in the trochlea by 1 5° knee flexion .

Figure 18-27 CT scan of lateral patellar tilt and displacemenr with the knee in 40

flexion. Precise midpatellar transverse CT images at 0°, 1 5° , 30° , and 45° knec flcllion give an accurate imprcssion of patellar alignment.

(From McConneJJ J , Fulkerson J: The knee: patcllofemoral and soft

tissue injuries. In Zachazcwski JE, Magee Dj, Quillen WS, editors:

Athletic injuries and rehabilitation, p 709, Philadelphia, \ 996, WB

Saunders.)

Magnetic Resonance Imaging

Early magnetic resonance imaging (MIU ) had limited value in the evaluation of patients with patellofemoral pain. The use of MRI was prohibitive, based on time and expense and on the quality and usefulness of the information obtained about patellar position and tracking. More recently, however, CT and MRI have been used to image the patellofemoral ( PF ) joint during active or dynamic flex­ion and extension activities. 57, 1 34, 1 7 1 , 1 72 Kinematic and conventional modes of MRI of the PF joint offer advan­tages over CT in tllat they do not require radiation, and they allow depiction of important passive and active soft issue stabilizers of the PF joint.57, 1 34, 1 7 1 It has been sug­gested that dynamic or kinematic MRI, which allows assess­ment of tlle contribution of activated muscles and other soft tissue structures, is more sensitive tllan static imaging for demonstrating PF alignment and tracking abnormal­ities. 57, 1 33, 1 69 Statistically significant differences in patellar tracking patterns and imaging parameters (e .g . , patellar tilt angle, bisect offset, lateral patellar displacement) between active and passive knee extension have been demonstrated by Brossmann et a1 . 1 7 1 To date, constraints have been encountered in tlle form of image acquisition time ( i .e . , 0.5 to 1 images/sec ) .57, 1 34, 1 71 The use of echoplanar MRI in the future may dramatically reduce image acquisi­tion time and greatly improve resolution, allowing images of moving or changing structures to be acquired at near real-time rates of l O to 1 6 frames/sec. 1 73

Bone Scan

A bone scan can reveal whether true intraosseous dysfunc­tion is present and may localize the source of pain. A posi­tive bone scan after knee trauma objectifies the problem. It may even demonstrate whether there is more activity proximally or distally in the patella and may reveal a prob­lem in the trochlea or elsewhere. Dye et al. J 74 have been particularly influential in emphasizing the dynamic hmc­tion of bone in patellofemoral pain and the usehllness of following this with bone (radionuclide) scans.

Conservative (Nonoperative) Treatment

The treatment of PFP should be dictated by objective data obtained through a thorough examination. Treatment decisions also should be based on a solid scientific and biomechanical rationale. Once the examination has been completed, data should be compiled and a hypothesis for­mulated regarding the cause of the pain. The clinician should attempt to classify patients based on whether the suspected mec11anism is a result of local PF joint dysfunc­tion, lower quarter dysfunction, or overuse. Treatment decisions should focus on the identified impairments.

Treatment Classification for Patellofemoral Pain Based on Mechanism

• Local patellofemoral joint dysfunction

• Lower quarter dysfunction

• Overuse

Patellofemoral Joint Dysfunction

Specific treatment strategies for patellar malalignment and/ or altered PF joint mechanics should be based on identified causes. As mentioned previously, possible contributing fac­�ors are bony and structural abnormalities, tightness of lateral structures, decreased patellar mobility, and quadri­ceps muscle weakness. From a rehabilitation standpoint, little can be done to correct bony deformities. Altllough the effects of the Q angle can be minimized through the interventions described below, conditions such as patella alta, trochlear dysplasia, femoral anteversion, and a laterally displaced tibial tuberosity are likely to require surgical intervention.

Tightness of Lateral Structures If tightness of the lateral retinaculum is found to be contri­buting to ELPS or lateralization of the patella, treatment interventions should include soft tissue mobilization tech­niques (e.g., passive stretch, transverse frictions, deep tissue massage) to increase extensibility. Soft tissue techniques in the area of the ITB and its interdigitation with the lateral

Figure 18-28

Patellofemoral Joint • C HAPTER 1 8 625

Soft tissue techniques in the area of the iliotibial band and its

interdigitation with the lateral retinaculum may prove useti.d for

increasing patellar mobility. The arrow indicates the line of force

application.

retinaculum may prove usehd (Figure I S -2S) . Because the ITB is a very dense, fibrous tissue, some question whether tllis structure can be stretched; however, longitudinal deep tissue massage may facilitate the breaking up of adhesions between the ITB and the overlying fascia.

Stretching of the tensor fascia lata also should be consid­ered, because tllis muscle can influence the tension in tile ITB (Figure I S-29) . Also, patellar mobilization and patellar taping techniques (discussed in a later section) can be used for passive stretching of the lateral structures. Low level, prolonged passive stretching is preferred so as to take advantage of tile creep effect of soft tissue.

Decreased Patellar Mobility Patellar oscillatory mobilization techniques combined with passive stretching should be performed to improve patellar mobility superiorly and inferiorly, as well as medially and laterally (see Figure I S-29) . If the patella lacks normal mobility, forces may be concentrated in localized areas. The most common reasons for reduced patellar mobility are prolonged immobilization, postoperative scarring, and quadriceps tightness.

When oscillatory mobilization techniques are per­formed, care should be taken to prevent excessive patellofe­moral joint compression. To facilitate mobilization of the patella, the knee should be in extension or only slightly flexed (Figure I S-30) . If the knee is flexed beyond 20° , the patella becomes seated within the trochlear groove,

626 C HAPTER 1 8 • Patellofemoral Joint

Figure 18-29 Self-stretch of the tensor fascia lata (TFL) muscle. Tllis muscle can

influence the patellofemoral joint through its insertion into the iliotibial band. The arrow indicates the line of force application by the

contralateral heel.

Figure 18-30 Patellofemoral joint mobilization techniques. Examples of medial glide (top) and inferior glide (bottom) . Care should be taken to prevent

direct joint compression. The arrows indicate the lines of force

application.

and passive tension of the quadriceps muscle limits mobility of the patella. Generally speaking, an inferior glide of the patella faci litates knee flexion, whereas a superior glide of the patella facilitates knee extension. Mediolateral patellar mobilization restores the normal patellar translations that occur during knee flexion and extension.

Tightness of the quadriceps causes the patella to be pulled superiorly, limiting the amount of inferior gliding of the patella during knee flexion . For this reason, stretch­ing of the quadriceps in the prone position should be con­sidered in combination with inferior patellar mobilization.

Quadriceps Muscle Weakness or Inhibition Rehabilitation of the extensor mechanism continues to play a significant role i n the treatment of PFP. With quadri­ceps muscle inhibition, pain and swelling must be con­trolled before a quadriceps exercise program is initiated. Pain modalities (e .g . , transcutaneous electronic stimulation [TENS]) , as well as methods to minimize effusion (e.g. , ice, electrical stimulation ), should be used as necessary.

As mentioned previously, the treatment of PFP using therapeutic exercise has focused on restoring dynamic patellar stability through strengthening of the VMO. Such clinical practice is based on the assumption that the VMO is disproportionately weak relative to the VL, even though the strength of the VMO cannot be quantified in vivo.

Theories on VMO Strengthening. The concept of VMO strengthening is based on the belief that the VMO can be selectively recruited, independent of the VL, through various exercises.7, 1 1 2 , 1 75 The most common activities that have been postulated to facilitate VMO strengthening are various quadriceps muscle exercises ( i .e . , straight leg raises, isometric quadriceps sets, terminal knee extension), hip adduction, and medial tibial rotation.

A thorough review of the existing literature shows that isolated contraction of the VMO, independent of the VL, has never been documented. 1 76 This finding suggests that isolated recruitment of the VMO does not occur with exer­cises that are commonly prescribed for the treatment of PFP and that selective strengthening is unlikely. Even if greater EMG activity could be elicited in the VMO relative to the VL, the magnitude ofVMO contraction would have to be at least 60% of maximum to stimulate hypertrophy. l 77

As such, it appears that isolated recruitment or strengthen­ing of the VMO through selected exercises may not be a realistic goal and that any emphasis on selective strengthen­ing of the VMO most likely translates into a general quad­riceps muscle strengthening effect.

General Quadriceps Muscle Strengthening. Con­vincing evidence indicates that improving quadriceps mus­cle strength is an important aspect of treatn1ent for PFP. A recent study by Natri et al. 1 78 revealed that restoration of quadriceps muscle strength was a significant predictor of improved long-term outcomes ( 7 -year follow-up) . Further­more, work by Powers et al. 1 79 suggested that enhanced

locomotor function in individuals with PFP is associated with increased torque of the quadriceps femoris muscle, which lends support to the concept of strengthening as a useful treatment option.

Despite the apparent benefits of quadriceps muscle reha­bilitation in patients with PFP, the mechanism by which strengthening improves PFP symptoms and functional abil­ity has not been established. General quadriceps muscle strengthening may improve patellar tracking, but a more plausible reason may a subtle alteration in the contact loca­tion and pressure distribution, possibly relieving sensitive areas.

The goal of tlle therapeutic exercise program should be to facilitate quadriceps muscle strengtll while minimizing patellofemoral joint stress. Clinicians can benefit from an understanding of tlle biomechanics of weight-bearing and non-weight-bearing exercises, two metllods commonly used to strengthen tlle extensor mechanism.

Weight-Bearing Versus N on-Weight-Bearing Exercises. During non-weight-bearing knee extension ( i .e . , resistance applied at tlle ankle), the amount of quadri­ceps muscle force required to extend tlle knee steadily increases as the knee moves from 90° to full knee exten­sion . 1 76 This increase in force is attributed to a decrease in mechanical advantage of the extensor mechanism. I S O

In addition to tlle increase in quadriceps muscle force as the knee extends, the patellofemoral contact area steadily decreases. This combination of increased quadriceps muscle force and decreased contact area during terminal knee exten­sion results in greater PF joint stress and pressure, compared to greater knee flexion angles in which the quadriceps muscle force is not as great and the contact area is larger. 1 76

Conversely, during weight-bearing exercises ( i . e . , squat­ting), the quadriceps muscle force is relatively minimal, when the knee is extended and steadily increases as the knee flexes. 1 76 The increase in force is distributed over a greater surface area, because the contact area also increases as tlle knee flexes. The greater contact area prevents excessive PF joint pressure during flexed knee activities. 1 76

Based on the biomechanics of the PF joint, non-weight­bearing exercises such as straight leg raises and terminal knee extensions should be avoided, as should weight­bearing activities such as deep squatting. These recommen­dations are supported by the work of Steinkamp et al . , l S I

who reported that greater patellofemoral stress was evident during a weight-bearing exercise ( leg press) at 48° to 90° knee flexion and during a non-weight-bearing exercise (knee extension) at 48° to 0° knee flexion ( Figure 1 8- 3 1 ) .

Quadriceps muscle strengtllening apparently can be per­formed safely throughout the 0° to 90° knee flexion range by varying the mode of exercise. Both weight-bearing and non-weight-bearing exercises can be used to promote quadriceps muscle hypertrophy; therefore a comprehensive strengtllening program probably should incorporate both types so that strengtllening can be performed throughout

Cil [L

� (/) (/) � (jj c Q, � 0 E

� Qi 1ii [L

Figure 18-31

Patellofemoral Joint • C HAPTER 1 8 627

30

20

1 0

o

... Leg press + Leg extension

30 48.4 60

Knee flexion (Degrees)

90

Patcllofemoral joint stress as a function of knee angle during open and

closed chain activities. The greatest stresses occur at high knee flexion

angles during closed chain activities and at low knee flexion angles

during open chain activities. ( From Steinkamp LA, Dillingham, Markel MD et aI: Biomechanical considerations in patellofemoral joint

rehabilitation, Am J Sports Med 21 :438-444, 1 99 3 . )

a large arc of motion. The data of Steinkamp et al . 1 8 1

can be used as a general guideline, but tlle exact exercise prescription will vary from patient to patient.

Electromyographic Biofeedback as an Adjunct to Strengthening. EMG biofeedback can be a valuable tool for helping the patient facilitate contraction of the quadri­ceps muscle . For example, patients can be instructed to monitor their quadriceps muscle activity while performing functional tasks such as step-downs and partial squats. The goal is to provide patients with immediate feedback to increase general quadriceps muscle recruitment, especially during eccentric contractions ( Figure 1 8-32 ) . Although comparison of raw EMG signals between muscles ( i .e . , to document "muscle imbalance" ) is not appropriate, 1 76

EMG biofeedback can be a useful tool for assessing general quadriceps muscle activation .

Taping and Bracing as an Adjunct to Strengthening. External patellar supports are commonly used in the man­agement of PFP, typically as an adjunct to other treatment methods ( e .g . , strengtllening) ?,8, 1 l - 1 3 The primary goal of PF joint bracing and taping is to centralize the patella within the trochlear groove, tllllS improving patellar track­ing. 8,1 82 The various patellofemoral braces on the market have used a number of methods to improve patellar track­ing, including neoprene sleeves with patellar cutouts, lateral buttresses, air bladders, and various Velcro straps ( Figure 1 8-33 ) . The patellar taping technique described by McConnelf has gained widespread clinical acceptance

628 C HAPTER 1 8 • Patellofemoral Joint

Figure 18-32 Electromyographic biofeedback can be used to facilitate quadriceps recruitment during functional tasks.

as an effective treatment option ( Figures 1 8 -34 and 1 8 - 3 5 ) . In this protocol, rigid strapping tape is applied to the patella to correct malal ignment ( as determined by clin­ical evaluation ), followed by functional strengthening of the quadriceps muscle . Various clinical studies support the therapeutic success of use of external patellar supports in conjunction with other treatment methods. 7,8 , 1 83 , 1 84

The fact that the various forms of external patellar sup­ports have proved effective in reducing symptoms imme­diately after application1 61 ,1 85 indicates that such orthoses have a mechanical effect on the patellofemoral joint. Although the literature supports the premise that bracing and/or taping reduces patellofemoral pain, the mechanism underlying this pain reduction does not appear to be related to changes in patellar tracking. For example, kinematic MRI studies have shown that patellar bracing has little effect on patellar track­ing. 1 86, 1 87 However, alternative mechanisms have been pro­posed. Using high resolution MRI, Powers et al . 1 88 reported tllat patellar bracing had only a small influence on patellar alignment ( lateral tilt and displacement); however, large increases in contact area between the patella and the trochlear groove were observed ( Figure 1 8-36) .

From a biomechanical standpoint, any increase in con­tact area distributes the forces over a greater surface area,

Figure 18-33 Patellofemoral joint brace used to control excessive lateral patellar tracking (True- Pull, Don Joy Orthopaedics Vista, CAl. The proximal and inferior straps attached to the lateral buttress (right) are designed

to limit lateral patellar displacement.

thereby reducing joint stress ( i . e . , force per unit area) . The results of the study by Powers et al. 1 88 suggest that changes in patellar alignment, by themselvo::s, may not be responsible for the alleviation of pain with bracing. A fol­low-up study by the same authors confirmed this hypoth­esis. 1 89 Biomechanical modeling methods were used to demonstrate that application of a patellofemoral brace resulted in a reduction in both pain and patellofemoral stress in individuals with long-standing symptoms. The reduction in stress was reported to be related to an increase in the PF joint contact area ( as determined with M RI ) . Taken together, this research suggests that patellar bracing or taping is effective in reducing symptoms in patients with patellofemoral pain; however, the underly­ing mechanism for this pain reduction may not be as previously believed.

The literature makes it clear tllat external patellar sup­ports can offer pain relief. This is significant from a clinical standpoint, because pain may influence quadriceps muscle inhibition. If the goal of conservative treatment of PFP is strengthening of the extensor mechanism, pain reduction is likely to facilitate recruitment of the quadriceps muscle. Such a reduction in pain allows for adequate exercise progression and subsequent muscle hypertrophy.

B

C

� i/l'

Figure 18-34 Correction of posterior and lateral tilt of the patella. A and B, To

correct an inferior tilt, tape is placed on the superior half of the patella.

An anteroposterior force is exerted on the superior aspect of the

patella to lift the inferior pole away form the infrapatellar fat pad. A and C, To correct a lateral tilt, 3a1teroposterior pressure is placed on

the medial half of the patella to lift the lateral border away from the

femur. (From McConnell ), Fulkerson J: The knee: patellofemoral and soli: tissue injuries. In Zachazewski ]E, Magee D], Quillen WS,

editors: Athletic injuries and 1'ehabilitation, p 7 1 5 , Philadelphia, 1 996,

WE Saunders . )

Figure 18-35

Patellofemoral Joint • C HAPTER 1 8 629

Correction of patellar glide. A and B, Tape is placed just lateral to the

lateral border of the patella and is used to glide the patella medially in

the femur. The clinician's thumb helps glide the patella medially, if

necessary, while the fingers pull the skin toward the patella, creating a wrinkle effect. Tape is anchored on the posteromedial aspect of the

medial condyle. Tape is not brought into the popliteal fossa, because

this may irritate the skin in this area ( From McConnell ) , Fulkerson J : The knee: patellofemoral a n d soli: tissue injuries. In Zachazewski JE,

Magee DJ, Quillen WS, editors: Athletic injuries and 1'chabilitation,

p 7 1 5, Philadelphia, 1 996, WE Saunders.)

Lower Extremity Dysfunction

In considering a treatment approach for abnormal lower extremity motions, it is important that the clinician keep in mind that altered mechanics can be driven from the foot upward or from the hip and pelvis downward. The ultimate goal in treatment of the lower extremity is to restore nor­mal dynamic alignment and function . In many cases, inter­ventions should be applied to both ends of the kinetic chain for maximum benefit.

630 C HAPTER 1 8 • Patellofemoral Joint

Abnorl11al Foot Pronaffon The decision on whether to use foot orthotics to control abnormal foot pronation should be based on a careful examination of the patient's gait or running pattern (or both ) . Patients who show abnormal pronation and corre­sponding medial rotation of the tibia and femur are can­didates for orthotics. If the patient shows excessive pronation but that motion does not appear to be trans­ferred proximally ( i .e . , it is absorbed at the talocrural joint), orthotics may have little benefit. The clinician may want to consider a temporary orthotic to evaluate whether tllis approach is effective.

The clinical usefulness of orthotics in tl1e treatment of PFP has been demonstrated by Eng and Pierrynowski. l 9o

Their study found tl1at both the orthotic group and the control group had significant reductions in pain after 8 weeks and that tl1e orthotic group had significantly greater pain reduction tl1an the control group.

Apart from foot orthotics, stretching of the calf muscles and strengthening of tl1e tibialis posterior should be con­sidered . Tightness of the calf muscles may result in abnor­mal pronation to compensate for the lack of normal ankle dorsiflexion during midstance. Because the tibialis posterior is the primary dynamic controller of pronation and the larg­est contributor to foot resupination in late stance, weakness of this muscle may lead to abnormal function of the foot and lower extremity.

Abnorl11al Hip Medial Rotation and Adduction If the femur is seen to "collapse" into medial rotation and/ or adduction during the dynamic examination and this motion appears to originate from the hip or pelvis ( as opposed to being influenced by tibial rotation), strengtl1en­ing of the lateral rotators and abductors of the hip may be indicated . With excessive medial rotation, tl1e emphasis

Figure 18-36 Axial M Rl scans of the patellofemoral joint

showing increased an patellofemoral joint contact

area after bracing. Note the increase in cartilage on

cartilage contact ( i .e . , white on white) in the

braced condition. M, Medial; L, lateral.

should be on tl1e gluteus maximus, because tl1is muscle is optimally suited to control medial rotation of the femur. The posterior fibers oftl1e gluteus medius and the deep rota­tors also contribute to dynamic stability of the femur; how­ever, their lateral rotation torque capability at tl1e femur is minimal in comparison. With excessive abduction, the focus should be on tl1e gluteus medius. The upper fibers of the gluteus maximus also have an abduction component and should be addressed if excessive adduction is observed.

Patients should be placed on an exercise program that focuses on pelvic stability during tl1e performance of active lower extremity movements. According to Nadler et al . , 1 9 1

it i s important to establish satisfactory lumbopelvic control to ensure tl1at tl1e proximal attachment sites for the abduc­tors and lateral rotators are stable. Mascal et al. l 92 outlined a three-phase treatment progression to enhance proximal control.

Treatment to Enhance Hip Control (Phase 1 ). Before dynanlic weight-bearing strengthening of the hip musculature is started, patients should perform nOI1-weight-bearing exercises of the hip abductors and exten­sors. When performing strengthening exercises for tl1e gluteus medius, the patient must take care to minimize the contribution of the tensor fascia lata, because contrac­tion of tl1is muscle contributes to medial rotation of tl1e lower extremity. This is best done witl1 the hip in lateral rotation (Figure 1 8-37) . Once tl1C patient can isolate tl1e muscles of interest in non-weight-bearing exercises while maintaining a stable pelvis, progression to weight-bearing activities can begin.

Treatment to Enhance Hip Control (Phase 2). Weight-bearing exercises should include exercises per­formed in bilateral and single-limb stance. At this time, tl1e patient should be introduced to the concept of neutral lower extremity alignment. This involves alignment of the

Figure 18-37

Patellofemoral Joint • C HAPTER 1 8 631

Side lying (clam) exercise to strengthen the gluteus medius. Note that the h.ip rotates externally during

abduction.

lower extremity such that the ASIS and knee remain posi­tioned over the second toe, with the hip positioned in neu­tral (Figure 1 8-38) . Postural alignment and symmetrical strengthening should be emphasized during all exercises (Figure 1 8-39) .

If the patient has a difficult time maintammg proper lower extremity alignment during the initiation of weight­bearing exercises, femoral strapping can be used to provided kinesthetic feedback and to augment muscular control and proprioception (Figure 1 8 -40) . Having patients perform weight-bearing exercises in front of a mirror can be useful. Also, taping or bracing of the PF joint may be used if pain is limiting the patient's ability to engage in a meaningful weight-bearing exercise program.

Treatment to Enhance Hip Control (Phase 3 ) . Once the patient can perform weight-bearing activities with­out pain and with neutral lower extremity alignment, exercises can be progressed to become more dynamic and functional. Maintenance of optimum lower extremity alignment can be reinforced by securing a Thera-Band around the distal aspect of the thighs to encourage activation of the lateral hip rota­tor/abductor musculature throughout the range of hip flex­ion/extension movement ( Figure 1 8-4 1 ) . Patients should be encouraged to return to their sport or activity gradually once they can achieve satisfactory dynamic control . With competitive or recreational athletes who will be returning to fujI participation, plyometric u-aining ( i .e . , jump training) should be considered as part ofth.is transition period.

Figure 18-38 Weight-bearing activities such as the single-leg squat, shown here,

should be done with particular attention given to proper alignment of

the pelvis, hip, knee, and ankle.

632 CHAPTER 1 8 • Patellofemoral Joint

Figure 18-39 A Thera- Band can be used to facilitate appropriate muscle action to ensure normal lower extremity alignment during weight-bearing activitics.

Abnormal Gait Deviations Facilitation of normal gait function is an essential compo­nent of the overall treatment plan . This is particularly important for the athlete ( especially runners) , in whom even a slight gait deviation can be exaggerated and can lead to injury at other j oints. Clinicians should pay partic­ular attention to reversal of the quadriceps avoidance gait pattern (walking with the knee extended or hyperex­tended ) . Because knee flexion during weight acceptance is critical for shock absorption, this key function must be restored to prevent the deleterious effects of high impact loading.

As noted previously, the primary causes of quadriceps avoidance are pain , effusion, and quadriceps muscle weak­ness. As these components are addressed in other aspects of treatment, the clinician should keep in mind that reso­lution of symptoms may not readily translate into a more "normal" gait pattern. This is particularly evident in a patient with long-term pain and dysfunction. Movement patterns can be "learned," and the patient may need to be "re-educated" with respect to key gait deficiencies. EMG biofeedback can be an effective tool for this pur­pose, because visualization of quadriceps muscle activity can augment the reversal of the quadriceps avoidance gait pattern.

Figure 18-40 Femoral strapping (SERF Strap, Don Joy Orthopaedics Vista, CAl can be used to improve lower extremity control and kinematics during the rehabilitation program and fi.lllctional activities.

Hip abductor action can be facilitated during a lunge task by creating

an adduction force that the patient is instructed to counteract.

Overuse

A lack of significant findings on the physical examination ( i .e . , normal patellar mechanics, normal lower extremity function) suggests that the source of symptoms may be related to overuse . This is typically the case in athletes. The treatment of choice for these individuals is control of symptoms and/or effusion, combined with rest and activity modification. Muscle sU'etching and bracing of the patella also can be used if indicated . Reducing the repetitive forces applied through the joint allows ?ealing of involved struc­tures. Return to activity should be gradual and closely monitored. The training regimen should be evaluated for obvious errors, such as increasing exercise intensity too quickly and not allowing adequate time for recovery. When extended time off is required, quadriceps and hip muscle strength should be maintained through careful application of resistive exercises (see the previous discussion) .

Surgical Considerations

Conservative treatment for patellofemoral pain may fail, even with the best physical therapy, medical management, bracing, and modification of activity. Some mechanical disorders of the knee extensor mechanism are too severe to respond fully to nonoperative treatment. Conditions that may resist non operative U'eatment include persistent patellar tilt, with or without chondrosis or subluxation; pathological plica; infrapatellar contracture; severe post­traumatic chondrosis-arthrosis; postoperative neuroma or scar pain; and recurrent dislocation. A tendency has arisen to use lateral release to treat any persistent anterior knee pain problem, rather than identifying a specific procedure to correct the underlying abnormality. This approach is not acceptable; lateral release is appropriate only to relieve objectitlable tilt of the patella when nonoperative measures have failed .

Patellofemoral Joint Problems Requiring Surgery

• Persistent patellar tilt

• Pathological plica

• Infrapatellar plica

• Severe post-traumatic chondrosis/arthrosis

• Postoperative neuroma

• Scar pain

• Recurrent dislocation

Obtaining a complete history before surgery is impera­tive. The clinician should determine what caused the onset of pain or instability. Was there a history of trauma, and is there any suggestion of generalized arthritis, referred pain, underlying structural deformity, or secondary pain? The clinician also should gain a feeling for the patient's

Patellofemoral Joint • C HA PTER 1 8 633

personality; patients with dependent personalities are less likely to improve. If the onset of pain is spontaneous, the patient is more likely to have an underlying structural malaJignment. The clinician should establish whether the primary problem is instability of the patella ( i . e . , subluxa­tion or dislocation ) or pain . If the problem is primarily pain, the clinician should determine whether it is more intra-articular or periarticular.

The physical examination is similar to that for a patient being evaluated for nonoperative treatment; however, greater emphasis is placed on identifying the specitlc source or sources and mechanical origin or origins of pain, impairment, and dysfunction that require sm-gical intervention and that would not respond to conservative management. 1 93, 1 94

The knee should be evaluated for evidence of patellar tilt, skin change, surgical scars, excessive varus or valgus, and contracture. The peripatellar retinaculum, patellar ten­don, distal quadriceps, and infrapatellar area must be exam­ined closely for evidence of neuroma, pain, and contracture. AJI surgical scars, including arthroscopy portals, should be palpated for induration and tenderness. Running a thumbnail along the scar easily determines pain (which, if present, suggests scar neuroma). If the patient has had previous surgery, direct palpation should be performed to determine whether a tender residual band of the lateral ret­inaculum is present. Patellar alignment should be evaluated actively and passively. The examiner should tlrmly press on the patella to determine whether pain occurs on compres­sion that reproduces the patient's complaints of discomfort. Pain reproduced by compression suggests articular cartilage breakdown.

The examiner also should note the degree of knee flex­ion pain or crepitation, because this helps localize a painful articular lesion (proximal lesions are painnd in tlexion past 75° to 80° , whereas distal lesions are painful close to fu ll extension) . Any evidence of tilt or subluxation should be noted. I n particular, the clinician must attempt to elevate the lateral patella away from the lateral u·ochlea to deter­mine whether tethering of the patella laterally is present. Any alteration of normal skin temperature should be noted, such as might occur with reflex sympathetic dystrophy. The surgeon must take into consideration all diagnostic imaging studies in determining the significance of tilt or subluxation.

At the conclusion of the preoperative evaluation, the clinician should decide whether surgical treatment offers the patient a reasonable hope of improvement. A specific, correctable problem that can be defined must be identitled . Is it tilt? Is arthrosis or chondrosis present, and if so, where is the lesion located? Is there a specific tender band of reti­naculum or patellar tendon? Does the patella track laterally so that the extensor mechanism needs to be realigned (in addition to lateral release )? Is there any evidence of neu­roma or scar pain from previous surgery? I s the pain related to malalignment or is it post-traumatic pain?

634 C HAPTER 1 8 • Patellofemoral Joint

lateral Release

Specific indications exist for lateral retinacular release, and many patients with resistant anterior knee pain do not respond to lateral retinacular release but can benefit from other surgical procedures. Surgical release of the lateral reti­naculum is used to reduce a pathological patellar tilt (greater than 1 2° ) in an individual with anterior knee pain who has minimal evidence of articular degeneration or subluxation. Lateral release is not an appropriate procedure for treating many patients with significant instability ( i . e . , subluxation or dislocation) of the patella-extensor mechanism. Lateral release has been (and occasionally still is) recommended to treat patellar subluxations; however, axial radiography, CT, and laboratory studies using a cadaver knee model have clearly shown that lateral release does not consistently relieve signs and symptoms of patellar subluxation.30, 1 95

Lateral release is not generally effective in relieving pain related to articular degeneration of the patella. 1 96 Once the lateral facet of the patella has collapsed and degenerated,83

releasing the lateral retinaculum does about as much to relieve contact stress on tile degenerated cartilage as releas­ing tile medial collateral ligament of a patient with medial compartment knee arthritis.

The clinician must also recognize that a lateral release is unlikely to effect any meaningful change in a normally aligned patella that has been severely traumatized (e .g. , fracture, dashboard injury) unless the patient has some sec­ondary retinacular contracture and resulting patellar tilt that needs release . Finally, lateral release, when done for tile wrong reason, can leave a patient with a debilitating medial patellar subluxation 197

Persistent Patellar Tilt

Some patients with pathological patellar tilt, with or without chondrosis or subluxation, do not respond to nonoperative treatment. In tllese patients, the appropriate surgical proce­dure is best determined after tile extent and location of artic­ular lesions have been considered and the knee has been evaluated for evidence of subluxation associated with tilt. In short, tilt with minimal evidence of articular degeneration or subluxation usually responds well to lateral release alone. 30 A possible exception is a patient with chondral soft­ening on the medial facet, because these patients may have greater contact pressure on soft cartilage after lateral release.

Postoperative rehabilitation is aimed at maintaining the mobility of tile lateral structures by taping the patella as soon as the sutures from tile arthroscopy site have been removed and keeping tile patella in the trochlea. Emphasis also must be placed on training of the gluteals to minimize any increase in tension in an overactive tensor fascia lata and a tight ITB.

If grade 3 or grade 4 articular breakdown198 is present on the lateral or distal medial facet in association with tilt, an

Figure 18-42 Transfer of the tibial tubercle. Anteromedial tibial tubercle transfer reduces contact stress on the patella while realigning the extensor

mechanism into a more medial orientation, thereby reducing or eliminating the likelihood of lateral patellar subluxation or dislocation.

( Redrawn from Fulkerson JP, Hungerford OS: Dis01'ders of the

patellofemoral joint, ed 2, Baltimore, 1 990, Williams & Wilkins. )

anteromedial tibial tubercle transfer (Trillat's procedure) is more effective than a lateral release/99,200 particularly willi any associated lateral patellar subluxation (Figure 1 8-42 ) . I f articular disease is not present but symptomatic subluxa­tion is associated with patellar tilt, Trillat's procedure may be most appropriate when all nonoperative measures to con­trol the instability have failed to provide adequate relieeOI

Pathological Plica

Nonoperative treatment fails in some patients because of a persistent pathological plica. Most significant pathological plicae occur in tile medial infra patellar region and can be readily identified on clinical examination. To make this diag­nosis, the clinician should be able to reproduce the patient's pain by palpating the plica; in most cases the plica is a prom­inent, palpable band. In tile autllors' experience, ariliro­scopic excision of a patllological plica results in relief of pain in most patients. However, Broom and Fulkerson202

noted that pathological plicae sometimes may be associated with patellar malalignment. In patients with plicae, there­fore, the examiner should be careful not to overlook other sources of pain related specifically to malalignment.

Infra patellar Contracture

Infrapatellar contracture may occur after trauma or surgery involving the anterior knee. Although classic patella baja may occur, some patients with more subtle infrapatellar contractu res may have persistent pain with relatively little evidence of contracture. Only a careful, pointed physical examination can detect this. Such patients usually have rather diffuse retropatellar tendon pain tllat frequently can be aggravated by squeezing or palpating the infrapatellar tendon area. An associated tightness of the medial and lateral retinaculum usually is noted.

In the authors' experience, once conservative rehabilita­tion fails, this condition must be evaluated ariliroscopically, and open release of tile contracture then is performed, usu­ally tllfough a short lateral incision. In most cases lateral release is necessary, which often reveals a dense, tight infrapa­tellar fat pad. Release of the fat pad allows tile surgeon to tilt the patella gradually up onto its medial edge, perpendicular to the trochlea. Complete release of infra patellar scars, metic­ulous hemostasis, and immediate postoperative knee mobili­zation to fu ll flexion are imperative in these patients. The results generally are excellent in properly selected patients when adequate release and debridement are performed.

Post-traumatic Chondrosis or Arthrosis

Time is particularly important in the treatment of patients who have sustained trauma to the anterior knee. The clini­cian should remember that intraosseous homeostasis can take 18 months or longer after injury.203 The clinician must carefully assess the degree of pain and whether the patient can reasonably tolerate a prolonged period of activity mod­ification and supportive management to allow spontaneous homeostasis. However, it is impossible to know whetller pain relief will be obtained after such a long period, and patients with more severe pain cannot always tolerate this much time without treatment. Supportive measures include repeated ice applications, nonsteroidal anti-inflammatory medications, bracing, taping, and reassurance. Exercising, particularly resisted knee extension, is counterproductive in some of these patients.

Once the decision has been made to operate, the prob­lem is whether the patella can be salvaged. Artllroscopic examination and debridement allow the surgeon to evalu­ate the extent of chondral injury once all soft tissue and retinacular problems have been solved. At the time of an initial artllroscopic procedure, any post-traumatic neuroma, indurate (painful) retinaculum or tendon, and dtickened plica or fibrillated articular cartilage should be excised. In most patients the lateral retinaculum need not be released unless a significant tilt aggravates the problem. Patellectomy is not commonly performed as the initial pro­cedure, because many patients may benefit from soft tissue ( retinacular) and articular debridement (chondroplasty) or

Patel/ofemoral Joint • C HAPTER 1 8 635

patellar realignment. If articular debridement has been performed, the clinician initially must avoid compression on the newly debrided area and must communicate with the surgeon to determine tile site of tile chondroplasty. Resurfacing of a severely damaged patella, sometimes in combination with an unloading tibial tubercle osteotomy, may be helpful in attempts to salvage the joint.203

I f arthroscopic treatment fails, a decision should be made as to whetller tile articular cartilage is sufficient to allow transposition of the tibial tubercle ( usually either medially, anteriorly, or bOtll) to shift contact stress from damaged to healtllY cartilage. In patients with extensive articular damage and intractable pain, patellectomy and patellofemoral resurfacing may be the only viable options. Resurfacing possibilities include autologous cartilage transplantation, allograft osteochondral transplantation, patellofemoral arthroplasty, and total knee replacement.

If healtllY cartilage is present proximally on tile patella, tile tibial tubercle may be moved anteriorly. If the best remaining cartilage is proximal and medial, the patella should be moved anteromedially. Long-term results with this procedure have been favourable.204 If the proximal patellar cartilage is severely damaged ( as it often is after a dashboard injury), tibial tubercle anteriorization is less likely to be successful . In this case, patellectomy or resurfacing may need to be considered.

Postoperative Neuroma or Scar Pain

A patient who has already had surgery and who complains of persistent pain that is different from the original pain may have a postoperative neuroma or painful scar. This is a clinical diagnosis, and it usually is not difficult to deter­mine as long as the examiner is looking for it. The thumbnail test ( running the dorsum of the thumbnail over each scar) elicits tile sharp pain of a neuroma in most cases. The clinician must make sure that this is not a diffuse sensitivity, suggesting reflex sympathetic dystrophy (RSD) . Patients with RSD are not surgical candidates and may require pain management programs, sympatlletic blocks, or surgical sympathectomy.

Sensitive scar or neuroma can be relieved transiently in the office by injection of a local anesthetic ( this confirms the diagnosis) . Administration of corticosteroids in conjunc­tion witll the local anestlletic does not usually provide lasting benefit to patients with a neuroma. In general, if nonopera­tive management has failed and the patient demonstrates a localized focus of pain in a scar, excision of tllis painful segment of tissue may be curative.

Recurrent Patellar Dislocation

Recurrent patellar dislocation can be devastating to the patel­lar articular cartilage, and tllis condition generally warrants early surgery if nonoperative treatment fails to restore stable

636 C HAPTER 1 8 • Patellofemoral Joint

tracking of the patella. Each patellar dislocation may result in a shearing off of articular cartilage from the medial patellar facet or lateral femoral trochlea. The cartilage may be stripped from the bone so that it cannot be replaced. Conse­quently, restoration of stable patellar tracking is important, preferably before serious cartilage damage occurs.

After an acute patellar dislocation, any fragment of artic­ular cartilage with bone attached should be replaced anato­mically, generally using an open lateral release incision and eversion of the patella to expose its medial facet for recon­struction. Very fine absorbable sutures (8-0 or smaller) may help approximate the cartilage edges.

In the authors' experience, patellar stability is best restored using a lateral release and tibial tubercle transfer as described by Trillat et al .2 1 and reviewed by Cox.z° 1

Overzealous medial imbrication (overlapping of free edges) poses a substantial risk of increasing contact pressure on the medial patellar facet (because the medial retinaculum is ori­ented so that its imbrication pulls the medial patellar facet posteriorly as well as medially) . If damage to the medial patella already is present after dislocation, anteromedial transfer of the tibial tubercle minimizes the load increase on the medial patella while reorienting the extensor mech­anism medially to minimize and hopefully eliminate the risk of lateral patellar dislocation.

In cases involving minimal subluxation, a specific advance­ment of the medial patellofemoral ligament ( MPFL), which interdigitates with the VMO, usually is enough to restore sta­bility. The MPFL remnant can be easily palpated through a small incision after the VMO has been lifted off the patella (Figure 1 8_43) .205,206 In our experience, after dislocation the MPFL remnant usually heals and provides a satisfactory

Figure 18-43 Palpation of the medial patellofemoral ligament.

structure for advancement, such that formal tendon transfer reconstruction of the MPFL is rarely indicated. Nonetheless, full MPFL reconstruction sometimes is needed. This proce­dure is technically demanding; small errors in graft placement can lead to overload and even late destruction of the PF joint.z°7 Tibial tubercle transfer should not be performed in a skeletally immature patient. Lateral release and careful MPFL advancement, properly performed, should provide adequate stability in most cases.

Summary

Surgical treatment can be extremely helpful in the manage­ment of patients with anterior knee pain resistant to nonop­erative treatment. It is most important to direct surgical treatment specifically to the precise cause of the knee pain. Painful articular lesions should be debrided and unloaded, painful segments of the retinaculum or scar excised, align­ment corrected, tilt relieved by lateral release, pathological plicae excised, and contractures released . Surgery should not be undertaken until the clinician has a clear concept of what needs to be corrected, and the patient understands the risks involved and the potential benefits. The chosen surgical procedure requires appropriate postoperative man­agement to optimize outcomes.

References

To enhance this text and add value for the reader, all refer­ences have been incorporated into a CD-ROM that is provided with this text. The reader can view the reference source and access it online whenever possible. There are a total of 207 references for this chapter.