knee biomechanic

KNEE BIOMECHANIC

SDr. Pukhrambam Ratan khuman (PT)

M.P.T., (Ortho & Sports)

April 11, 2023 Dr. Ratankhuman M.P.T., (Ortho & Sports) 2

introduction

Participating bones –FemurTibiaPatella


Knee complex

Tibio-femoral joint Patello-femoral joint


Tibio-femoral/Knee joint Ginglymus – (Hinge) ?

A freely moving joint in which the bones are so articulated as to allow extensive movement in one plane.

Arthodial – (Gliding) ? 6 degrees of freedom

3 Rotations3 Translations


Knee degree of freedom

RotationsFlex/Ext – 150 – 1400

Varus/Valgus – 60 – 80 in extensionInt/ext rotation – 250 – 300 in flexion

TranslationsAP 5 - 10mmCompression/Distraction 2 - 5mmMedial/Lateral 1-2mm


General Features of Tibio-femoral Joint Double condyloid knee joint is also referred to as Medial

& Lateral Compartments of the knee. Double condyloid joint with 30 freedom of Angular

(Rotatory) motion. Flexion/Extension – ○ Plane – Sagittal plane○ Axis – Coronal axis

Medial/lateral (int/ext) rotation –○ Plane – Transverse plane ○ Axis – Longitudinal axis

Abduction/Adduction – ○ Plane – Frontal plane ○ Axis – Antero-posterior axis.


Femoral articular surface

Femur is proximal articular surface of the knee joint with large medial & lateral condyles.

Because of obliquity of shaft, the femoral condyles do not lie immediately below the femoral head but are slightly medial to it.

The medial condyle extend further distally, so that, despite the angulation of the femur’s shaft, the distal end of the femur remains essentially horizontal.


In sagittal plane - Condyles have a convex shape In the frontal plane - Slight convexity The lateral femoral condyle

Shifted anteriorly in relation to medialArticular surface is shorter Inferiorly, the lateral condyle appears to be longer

Two condyles are separated –Inferiorly by Intercondylar notch Anteriorly by an asymmetrical, shallow groove called

the Patellar Groove or Surface


Tibial articulating surface Asymmetrical medial & lateral tibial condyles

constitute the distal articular surface of knee joint. Medial tibial plateau is longer in AP direction than

lateral The lateral tibial articular cartilage is thicker than

the medial side. Tibial plateau slopes posteriorly approx 70 to 100

Medial & lateral tibial condyles are separated by two bony spines called the Intercondylar Tubercles


9o

The tibial plateaus are predominantly flat, but convexity at anterior & posterior margins

Because of this lack of bony stability, accessory joint structures (menisci) are necessary to improve joint congruency.


Menisci of knee joint 2 asymmetrical fibro cartilaginous joint disk

called Menisci are located on tibial plateau. The medial meniscus is a semicircle & the

lateral is 4/5 of a ring (Williams, PL, 1995).


Both menisci are –Open towards intercondylar

areaThick peripherallyThin centrally forming

cavities for femoral condyle By increasing congruence,

menisci play in reducing friction between the joint segment & serve as shock absorber.


Meniscal attachment Common attachment of medial & lateral –

Intercondylar tubercles of the tibiaTibial condyle via coronary ligamentsPatella via patellomeniscal or patellofemoral ligamentTransverse ligament between two menisciAnterior cruciate ligament (ACL)


Meniscal attachment Unique attachment of medial menisci –

Medial collateral ligament (MCL)Semitendinous muscle

Unique attachment of lateral menisci –Anterior & posterior meniscofemoral ligamentPosterior cruciate ligament (PCL)Popliteus muscle


Young children whose menisci have ample of blood supply have low incidence of injury

In adult, only the peripheral vascularized region is capable of inflammation, repair & remodeling following a tearing injury.

Menisci are well innervated with free nerve ending & 3 mechanoreceptors (Ruffine corpuscle, Pacinian corpuscle & Golgi tendon organs)


TF alignment & weight bearing force The anatomic/ longitudinal axis –

Femur – Oblique, directed inferiorly & mediallyTibia – Directed verticallyThe femoral & tibial longitudinal axis form an angle

medially at the knee joint of 1850 – 1900, i.e. 50 – 100 creating Physiological Valgus at knee

In bilateral static stance – equal weight distribution on medial & lateral condyle


Deviation in normal force distribution – TF angle > 1900 – Genu Valgum – compress

lateral condyleTF angle < 1800 – Genu Varum – compress

medial condyle Compressive force in dynamic knee joint

2 – 3 time body weight in normal gait5 – 6 time body weight in activities (like –

Running, Stair Climbing etc.)


Knee joint capsule Joint capsule enclose – TF & PF is large lax Outer portion – firmly attached to the inferior aspect

of femur & superior portion of tibia. Posterior attachment

Proximally to posterior margins of the femoral condyles and intercondylar notch.

Distally to posterior tibial condyle. Anterior attachment

Superiorly – Patella, tendon of quadriceps muscles Inferiorly patellar tendon complete the anterior portion

of the joint capsule.


The antero-medial & antero-lateral portions of the capsule, are often separately identified as the medial and lateral patellar retinaculae or together as the extensor retinaculum.

The joint capsule is reinforced medially, laterally & posteriorly by capsular ligaments.


Extensor retinaculum

2 layers – superficial & deeper Deeper layer –

Connecting the capsule anteriorly to menisci & tibia via coronary ligament (known as patellomeniscal or patellotibial band)

Superficial layer – Mixed with vastus medialis & lateralis muscle &

distal continue to posterior femoral condyle (patellofemoral ligament)


Synovial lining The intricacy of fibrous layer

capsule is surpassed by its synovial lining except posteriorly.

Synovium adheres to anterior aspect & side to the ACL & PCL.

Embryologically, the synovial lining of the knee joint capsule is divided by septa into 3 separate compartment – Superior patellofemoral compartment2 separate medial & lateral

tibiofemoral compartment


Ligament of knee joint Collateral ligament

Medial collateral ligament (MCL)Lateral collateral ligament (LCL)

Cruciate ligamentAnterior cruciate ligament (ACL)Posterior cruciate ligament (PCL)

Posterior capsular ligament Meniscofemoral ligament Iliotibial band


MCL

Attachment – Origin – medial aspect of medial femoral

condyleInsertion – proximal tibia

Function –Resist valgus stress force (specially in

extended knee)Check lateral rotation of tibiaAlso restrain anterior displacement of tibia

when ACL is absent.

MCL


LCL Attachment –

Origin – lateral femoral condyleInsertion – posteriorly to head

of fibula Function –

Resist varus stress force across the knee

Check combined lateral rotation with posterior displacement of tibia in conjunction with tendon of popliteal muscle.


Cruciate ligament

Cruciate = “Resembling a cross” in Latin.

Located within the joint capsule & are therefore called Intracapsular Ligaments.

Cruciate ligament provide stability in sagittal plane

The ACL & PCL are centrally located within the capsule but lie outside the synovial cavity.

ACLPCL


ACL

Attachment –Origin – from anterior surface the tibia in the

intercondylar area just medial to medial meniscus. It spans the knee laterally to PCL & runs in a superior

& posterior direction Insertion – to posteriorly on lateral condyle of femur

ACL is divided into 2 bands – Antero-medial band (AMB)Postero-lateral band (PLB)


Function of acl Primarily –

Check femur from being displaced posteriorly on the tibia Conversely, the tibia from being displaced anteriorly on

femur. It tightens during extension, preventing excessive

hyperextension of the knee. ACL carried 87% of load when anterior translatory

force was applied to tibia with extended knee. Check tibial medial rotation by twisting around PCL ACL injury is common when knee is in flexed & tibia

rotated in either direction


PCL

Attachment – Origin – from posterior tibia in intercondylar area

and runs in a superior and anterior direction on medial side of ACL.

Insertion - to anterior femur on the medial condyle PCL is divided into 2 bands –

Antero-medial band (AMB)Postero-lateral band (PLB)


Function of pcl Primarily –

Check femur from being displaced anteriorly on the tibia or

Tibia from being displaced posteriorly on femur. It tightens during flexion & is injured much less

frequently than ACL. PCL carry 93% of load when posterior translatory

force was applied to tibia with extended knee. PCL play a role in both restraining & producing

rotation of the tibia.


Summary of ACL & PCL attachments –ACL – Runs from anterior tibia to posterior femur PCL – Runs from posterior tibia to anterior femur


Posterior capsular ligament

Oblique popliteal ligament Posterior oblique ligament Arcuate ligament:

Arcuate ligament lateral branchArcuate ligament medial branch


Oblique popliteal ligament

Attachment –Origin – The central part of posterior aspect of

the joint capsuleInsertion - Posterior medial tibial condyle

Function –Reinforces posteromedial knee joint capsule

obliquely on a lateral-to-medial diagonal from proximal to distal


Posterior oblique ligament

Attachment – Origin – Near the proximal origin of the MCL

and adductor tubercleInsertion – Posteromedial tibia, posterior capsule

& posteromedial aspect of the medial meniscus Function –

Reinforces the posteromedial knee joint capsule obliquely on a medial-to-lateral diagonal from proximal to distal


Arcuate LigamentLateral Branch Medial branch

Distal Attachment

From posterior aspect of the head of the fibula

Proximal Attachment

To tendon of popliteus muscle & posterior capsule

Into oblique popliteal lig on medial side of joint

FunctionReinforces the postero-lateral knee joint capsule

obliquely on a medial to lateral from proximal to distal


Meniscofemoral ligament (MFl)

There are 2 portions of MFL, at least one in 91% of knees & 30% knee having both.

MFL are not true ligaments because they attach bone to meniscus, rather than bone to bone.


Meniscofemoral ligament (MFl) Attachment –

Origin – Both originate from posterior horn of lateral meniscus

Insertion – to lateral aspect of medial femoral condyle ○ The “Ligament of Humphry” or “Antero-MFL” is the

ligament run anterior to PCL on tibia ○ The “Ligament of Wrisberg” or “Postero-MFL” is the

ligament run posterior to PCL, also known as “3rd Cruciate Ligament of Robert”

Function – They may assist PCL in restraining posterior tibial translationAlso assist popliteus muscle by checking tibial lateral rotation


Bursa associated with knee

Pre-patellar bursa – Located between the skin & anterior surface of patella They allows free movement of skin over patella during

knee flexion & extension Subcutaneous bursa –

Located between patellar ligament & overlying skin Deep infra-patellar bursa –

Located between patellar ligament & tibial tuberosityHelps in reducing friction between the patellar ligament

& tibial tuberosity


Function of knee joint

Osteokinemetic of knee joint – Primary motions – ○ Flexion / Extension○ Medial / Lateral Rotation

Secondary motions – ○ Antero-posterior displacement of femur or tibia○ Abduction / Adduction through valgus or varus force


Flexion & extension

Axis – no fixed axis but move through ROM (frontal axis)

Plan – sagittal plan ROM of flexion / extension –

Flexion – 1300 – 1400

Extension – 50 – 100 (Consider normal, beyond this termed as Genurecurvatum)

In close kinematic chain (OKC) – flexion / extension range is limited by ankle range.


Medial / lateral rotation

Axis – Longitudinal / Vertical axis Plan – Transvers plan ROM at 900 knee flexion –

Lateral rotation – 00 – 400

Medial rotation – 00 – 300


TF CKC Flexion

Early 00 - 250 knee flexion –Posterior rolling of femoral

condyles on the tibia As flexion continues –

Posterior Rolling accompanied by simultaneous Anterior glide of femur

Create a pure Spin of femur on the posterior tibia


TF CKC extension

Extension from flexion is a reversal of flexion motion.

Early extension –Anterior rolling of femoral

condyles on tibial plateau As extension continues –

Anterior Rolling accompanied by simultaneous Posterior glide of femur

Produce a pure Spin of femoral condyles on tibial plateau


Tf ock flexion / extension

When tibia is flexed on a fixed femur –The tibia performed Both Posterior Rolling &

Gliding on relatively fixed femoral condyles.

When tibia is Extended on a fixed femur –The tibia performed Both Anterior Rolling &

Gliding on relatively fixed femoral condyles.

April 11, 2023 49Dr. Ratankhuman M.P.T., (Ortho & Sports)

Locking & unlocking (screw home mechanism)


Locking of knee joint CKC femoral extension from 300 flexion –

Larger medial femoral condyle continue rolling & gliding posteriorly when smaller lateral side stopped.

These result in medial rotation of femur on tibia, seen in last 50 of extension.

The medial rotation of femur at final stage of extension is not voluntary or produce by muscular force, which is referred as “Automatic” or “Terminal Rotation”.

The rotation within the joint bring the joint into a closed packed or Locked position.

The consequences of automatic rotation is also known as “Locking Mechanism” or “Screw Home Mechanism”.

OKC – lateral rotation of tibia on fixed femur


Unlocking of knee joint

To initiate flexion, knee must be unlocked. A flexion force will automatically result in lateral

rotation of femur Because the larger medial condyle will move before

the shorter lateral condyle.Popliteus is the primary muscle to unlocked the knee.


Role of Cruciate Ligaments

in Flexion/Extension


TF CKC Flexion: ACL Control

At full extension –Angle of ACL

inclination greatestAnterior directed

component force will eventually Restrain Posterior Femoral Roll


TF CKC Flexion: ACL Control cont…

As TF flexion increases – Angle of ACL inclination

decreasesAnterior directed

component force increases sufficient enough to produce Anterior Femoral Slide


Hyperextension Impact on ACL

End ROM extension brings the mid-substance of the ACL in contact with the femoral intercondylar shelf (notch of Grant)

This contact point acts as a fulcrum to tension load the ACL


TF CKC Flexion: PCL Control

Angle Of PCL Inclination is greatest at full flexion.

Anterior directed component force will eventually Restrain Posterior Femoral Roll


TF CKC Extension: PCL Control

As TF extension increases –Angle Of PCL Inclination

decreasesPosterior directed component

force increases sufficient enough to Produce Posterior Femoral Slide


TF OKC Extension Arthrokinematics sagittal plan

Extension – Meniscal migrate Anteriorly – ○ Because of meniso-patellar

ligament

Menisco-patellar Ligaments


TF OKC flexion Arthrokinematics sagittal plan

Flexion – Menisci migrate posteriorly because of Semimembranosis attachment to medial meniscusPopliteus attachment to lateral meniscus


Knee axial rotation


Axial rotation of kneearthrokinemetic Axis – vertical axis Plan – transvers plan ROM – Maximum range is

available at 90 of knee flexion. The magnitude rotation diminishes

as the knee approaches both full extension and full flexion.

Medial condyle acts as pivot point while the lateral condyles move through a greater arc of motion, regardless of direction of rotation.


rotation of tibia During Tibial lateral rotation on the femur –

Medial tibial condyle moves slightly anteriorly on the relatively fixed medial femoral condyle, whereas lateral tibial condyle moves a larger distance posteriorly.

During tibial medial rotation –Medial tibial condyle moves only slightly

posteriorly, whereas the lateral condyle moves anteriorly through a larger arc of motion.


During both medial and lateral rotation – The menisci reduce friction & distribute femoral

condyle force created on the tibial condyle without restricting the motion.

Meniscus also maintain the relationship of tibia & femoral condyles just as they did in flexion and extension.


Valgus (Abduction)/Varus (Adduction) Axis – Antero-posterior axis Plan – Frontal plane ROM –

8 at full extension13 with 20 of knee flexion.

Excessive frontal plane motion could indicate ligamentous insufficiency


Patello-femoral joint (pfj)


pFj function

It work primarily as an anatomical pulley It reduce friction between quadriceps tendon

& femoral condyle. The ability of patella to perform its function

without restricting knee motion depends on its mobility.


PFJ articulating surface

The triangular shape patella is a largest sesamoid bone in body is a least congruent joint too.

Posterior surface is divided by a vertical ridge into medial & lateral patellar facets.

The ridge is located slightly towards the medial facet making smaller medial facet

The medial & lateral facet are flat & slightly convex side to side & top to bottom.

At least 30% of patella have 2nd ridge separating medial facet from the extreme medial edge known as Odd Facet of Patella.


Femoral articulating surface

Patella articulate in femur with intercondylar groove or femoral sulcus on anterior surface of distal femur.

Femoral surface are concave side to side & convex top to bottom but lateral facet is more convex then medial surface.


PFJ congruence

The vertical position of patella in femoral sulcus is related to length of patellar tendon, approximately 1:1 is (referred to as Insall-Salvati index)

An excessive long tendon produce an abnormally high position of patella on femoral sulcus known as patella alta.

In neutral or extended knee, the patella has little or no contact with the femoral sulcus beneath.


At 100 – 200 of flexion – contact with inferior margin of medial & lateral facet.

By 900 of flexion – all portion of patella contact with femur except the odd facet.

Beyond 900 of flexion – medial condyle inter the intercondylar notch & odd facet achieves contact for the first time.

At 1350 of flexion – contact is on lateral & odd facet with medial facet completely out of contact.


Patello femoral joint stabilizer


Medial-lateral PFJ stability

PFJ is under permanent control of 2 restraining mechanism across each other at right angel.Transvers group of stabilizerLongitudinal group of stabilizer


Transvers stabilizer – Medial & lateral retinaculumVastus Medialis & LateralisThe lateral PF ligament contributes 53% of total

force when in full extension of knee.


Longitudinal stabilization

Patellar tendon – inferiorly Quadriceps tendon – superiorly


Medial-lateral positioning of patella / patellar tracking When the knee is fully extended & relax, the

patella should be able to passively displaced medially or laterally not more then one half of patella.

Imbalance in passive tension or change in line of pull of dynamic structures will substantially influence the patella.

Abnormal force may influence the excursion of patella even in its more secure location within intercondylar notch in flexion.


Medial & lateral force on patella Since the action line of quadriceps & patellar

ligament do not co-inside, patella tend to pulled slightly laterally & increase compression on lateral patellar facets.

Larger force on patella may cause it to subluxation or dislocate off the lateral lip of femur.

Genu valgum increase the obliquity of femur & oblique the pull of quadriceps.


Femoral anteversion & tibial torsion creates an increased obliquity in patella predisposing to excessive lateral pressure or to subluxation or dislocation.

Excessive tension in lateral retinaculum (or weakness of VMO) may cause the patella to tilt laterally.

Insufficient height of lateral lips of femoral sulcus may create patellar subluxation or fully dislocation, even with relatively small lateral force.


Muscles of knee &

its function


Muscles of the KneeArea One-joint Muscle Two-joint Muscle

AnteriorVastus Lateralis

Rectus Femorisvastus MedialisVastus Intermedialis

Posterior Biceps Femoris (Short)

Biceps Femoris (Long)Semimembranosus

SemitendinosusSartoriusGracilis

GastrocnemiusLateral Tensor Fascia Latae


Muscles of Posterior Knee

Knee FlexorsSemimembranosus, Semitendinosus, Biceps Femoris (Long & Short Heads), Sartorius, Gracilis, Popliteus & Gastrocnemius Muscles

Flex + Tibial Medial Rotators

Popliteus, Gracilis, Sartorius, Semimembranosus & Semitendinosus Muscles

Flex + Tibial Lateral Rotator Biceps Femoris

Flex + Abductor

Biceps Femoris, Lateral Head Gastrocnemius & Popliteus

Flex + Adductor

Semimembranosus, Semitendinosus, Medial Head Gastrocnemius, Sartorius & Gracilis


Muscles

posterior

thigh


Knee flexor groups

7 muscles flex the knee [Semimembranosus, Semitendinosus, Biceps Femoris (Long & Short Heads), Sartorius, Gracilis, Popliteus & Gastrocnemius Muscles].

5 muscles of flexors (Popliteus, Gracilis, Sartorius, Semimembranosus & Semitendinosus Muscles) –They have the potential to medially rotate the tibia on a

fixed femurWhereas the biceps femoris is capable of rotating the

tibia laterally.


Knee flexor groups cont…

The lateral muscles (Biceps Femoris, Lateral Head of Gastrocnemius, & Popliteus) Capable of producing valgus moments at knee

The medial muscles (Semimembranosus, Semitendinosus, Medial Head of Gastrocnemius, Sartorius & Gracilis) Can generate varus moments


biceps femoris or Lateral Hamstring

Proximal attachments: By two heads: Long head – to the tuberosity of ischium, having

a common tendon of attachment with semitendinosus.

Short head – to the lower portion of shaft of femur & to lateral intermuscular septum.

Distal attachments: 2 heads unite to be attached to the head of fibula,

to the lateral condyle of the tibia & to the fascia of leg.

AXN: Hip extension & external rotation Knee flexion & external rotation.


Semitendinosus or medial hamstring

Proximal attachment: Tuberosity of ischium, having a

common tendon with the long head of the biceps.

Distal attachment: Medial aspect of tibia near the

knee joint, distal to the attachment of the gracilis.

AXN: Hip extension and internal

rotation Knee flexion and internal rotation.


semimembranosus

Proximal attachment: Tuberosity of the ischium

Distal attachment: Medial condyle of the tibia.

AXN: Knee flexion and internal rotation Hip extension and internal rotation.


Gastrocnemius

Proximal attachments: Above the femoral condyles and span the knee joint

on the flexor side. The muscular portion of the gastrocnemius may be

seen contracting in resisted flexion of the knee. Because the gastrocnemius is more important as a

plantar flexor of the ankle than as a knee flexor Distal attachments:

To the posterior calcaneus


Popliteus Proximal attachment:

By a strong tendon from the lateral condyle of the femur.

The muscle fibers take a downward medial course and are attached into proximal posterior portion of body of tibia.

Distal attachment: widespread in a proximal-distal direction,

giving the muscle a somewhat triangular shape. AXN:

Medial rotation and flexion of knee.


Muscle passing medial knee


Anterior Muscles

Quadriceps muscles comprise 4 muscles that cross the anterior kneeRectus femorisVastus lateralisVastus IntermedialisVastus Medialis


Quadriceps muscle Functions –

Together, the 4 components of quadriceps femoris muscle function to extend the knee.

Rectus femoris being a 2 joint muscle, it also involved in hip flexion along with knee extension.

Angle of pull of Quadriceps –Vastus lateralis – Pull 350 Lateral to long axis of femurVastus Intermedius – Pull Parallel to Shaft of femur, making purest

knee extensor. Vastus Medialis – Pull depended on segment of muscle –○ Upper fibers Vastus Medialis Longus (VML) angled 150 – 180 Medially○ Distal fibers Vastus Medialis Oblique (VMO) angled 500 – 550 Medially


Patellar Influence on Quadriceps Function Patella lengthens the MA of quadriceps by

increasing the distance of quadriceps tendon & patellar tendon from the axis of the knee joint.

The patella, as an anatomic pulley, deflects the action line of quadriceps away from the joint centre, increasing the angle of pull & enhancing extension torque generation.

Pull of quadriceps also creates anterior translation of tibia on femur increasing ACL restraint


Quadriceps activities During weight-bearing When an erect posture is attained –

Minimal activity of quadriceps because the LOG passes just anterior to knee axis results in a gravitational extension torque that maintains the joint in extension.

In weight-bearing with the knee slightly flexed –The LOG pass posterior to knee joint axis As the gravitational torque tend to promote knee

flexion, the activity of quadriceps is necessary to counterbalance the gravitational torque and maintain the knee joint in equilibrium.


LOG & Movement arm (MA) during squatting


Quadriceps activities during non–weight-bearing The MA of resistance is minimal when the knee

is flexed to 900 but increases as knee extension progresses.

Therefore, greater quadriceps force is required as the knee approaches full extension.

The opposite happens during weight-bearing activities.


LOG & Movement arm (MA) during non-weight bearing


Quadriceps Strengthening:Weight-Bearing versus Non–Weight-

Bearing Weight-bearing quadriceps exercises as squat

& leg press resulted in a posterior shear force at knee throughout the entire ROM

There was No Anterior Shear anywhere in the ROM.

In contrast, anterior shear force in a non–weight bearing knee extension exercise maximal anterior shear occurring between 200 and 100.


Quadriceps Strengthening:Weight-Bearing versus Non–Weight-

Bearing cont… A Posterior Shear Force was also found

during Non–Weight-Bearing Exercise, only between 600 and 1010 of flexion.

Weight Bearing Exercises are often prescribed after ACL or PCL injury because of less stressful, more like functional movements & safer than non–weight-bearing exercises.


Other muscles helping knee extension The actions of the Gluteus Maximus

& Soleus Muscles can influence knee motion in weight-bearing.

Although they do not cross the knee joint, these muscles are capable of assisting with knee extension.


Iliotibial Band or IT tract Proximally –

The IT band is from Tensor Fascia Lata (TFL), Gluteus Maximus & Gluteus Medius muscles.

Distally –Attach to lateral intermuscular

septum & inserts into the Anterolateral Tibia (Gerdy’s Tubercle).

IT band also attaches to patella via lateral PF ligament of lateral retinaculum.

ITB

GM

TFL


AXN:Reinforcing anterolateral aspect of knee jointAssisting ACL in checking posterior femoral or

anterior tibial translation when the knee joint is nearly full extension.

With the knee in flexion, the combination of IT band, LCL & popliteal tendon increases the stability of lateral knee.


AXN line for itb

In extended knee –IT band moves anterior to the knee joint axis.

In flexed knee –IT band moves posteriorly over the lateral femoral

condyle as the knee is flexed. The IT band, therefore, remains consistently

taut, regardless of hip or knee’s position.


Knee joint stabilizers


Stabilization of knee joint Classification of supporting structure of knee –

Functional – ○ Static stabilizer○ Dynamic stabilizer

Structural – ○ Capsular method○ Extra-capsular method

Location – ○ Medial joint compartment○ Lateral joint compartment


Static stabilizer

It include the passive structures, such as – CapsuleLigaments –○ Meniscopatellar lig, ○ PF lig, ○ MCL & LCL, ○ ACL & PCL, ○ Oblique poplitial & ○ Transverse lig.


Dynamic stabilizer

It includes following muscles & oponeuroses –Quadriceps femoris,IT band, Extensor retinaculum, Poplitius, Pes anserinus, Hamstrings and also Gastrocnemius


Medial joint stabilizers

Structure includes –Medial patellar retinaculum, MCL, Oblique poplitial ligament & PCL


Lateral joint stabilizers

The structure included in static & dynamic stabilization of knee – IT band, Biceps femoris, Popliteus, LCL, Meniscofemoral arcuate,ACL & Lateral patellar retinaculum


Knee Joint Stabilizers

Direction Structures Functions

A-P/Hyperextensionstabilizers

• Anterior cruciate ligament• Iliotibial band• Hamstring muscles• Soleus muscle (in weight-

bearing)• Gluteus maximus muscle

(in weight-bearing)Limit anterior tibial (or posteriorfemoral) translation• Posterior cruciate ligament

• Meniscofemoral ligaments • Quadriceps muscle• Popliteus muscle• Medial & lateral heads of

gastrocnemius


Knee Joint StabilizersDirection Structures Functions

Varus/valgus stabilizers

• Medial collateral ligament• Anterior cruciate ligament• Posterior cruciate ligament• Arcuate ligament• Posterior oblique ligament• Sartorius muscle• Gracilis muscle • Semitendinosus muscle• Semimembranosus muscle• Medial head of gastrocnemius muscle

Limits valgus of tibia

• Lateral collateral ligament• Iliotibial band• Anterior cruciate ligament• Posterior cruciate ligament• Arcuate ligament• Posterior oblique ligament• Biceps femoris muscle• Lateral head of gastrocnemius muscle

Limit Varus of tibia


Knee Joint Stabilizers

Direction Structures Functions

Internal/externalrotational stabilizers

• Anterior cruciate ligament• Posterior cruciate ligament• Posteromedial capsule• Meniscofemoral ligament• Biceps femoris

Limit medial rotation of tibia

• Posterolateral capsule• Medial collateral ligament• Lateral collateral ligament• Popliteus muscle• Sartorius muscle• Gracilis muscle

Semitendinosus muscle• Semimembranosus muscle

Limit lateral rotation of tibia


References

Joint Structure and Function: A Comprehensive Analysis, Fourth Edition, Cynthia C. Norkin, 2005

Joint Structure and Function: A Comprehensive Analysis, Third Edition, Cynthia C. Norkin

Clinical Kinesiology and Anatomy, Fourth Edition, Lynn S. Lippert, 2006

Basic Biomechanics of the Musculoskeletal System, third edition, Margareta Nordin

knee biomechanic

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