the knee: anatomy and injuries. 2 joints at the knee tibiofemoral joint – formed between tibia and...
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The Knee: Anatomy and Injuries
2 Joints at the Knee Tibiofemoral Joint – formed between
tibia and femur A HINGE JOINT Patellofemoral joint – formed
between the patella and the femur A GLIDING JOINT
Skeletal Anatomy Femurproximal – head and neck of
femur, greater trochanter
distal – medial and lateral condyles and
epicondyles
Patella – largest sesamoid bone in body
Tibia – tibial plateau forms knee joint with femur
The fibula is not a part of the knee joint
http://uwmsk.org/RadAnatomy.html
Muscles that move the knee and thigh The Quadriceps – Knee Extension
1. Vastus Medialis2. Vastus Lateralis3. Vastus Intermedius4. Rectus Femoris – 2 joint muscle that also acts as a
hip flexor http://www.bodybuilding.com/exercises/detail/view/name/leg-extensions
The Hamstrings- knee flexion
3 muscles:1. Biceps Femoris2. Semimembranosus3. Semitendinosus
http://www.bodybuilding.com/exercises/detail/view/name/lying-leg-curls
The Adductors (Groin)Adduct the thigh
1. Adductor Longus2. Adductor Magnus3. Adductor Brevis4. Gracilis
http://www.5min.com/Video/Adductor-exercise-1924
The Sartorius: - flexes,
abducts, and laterally rotates thigh
- longest muscle in the body, “tailor’s muscle”
- Crosses hip and knee joint
The Iliotibial Tract(IT Band)
- neither a muscle or tendon, but a long, thick band of tissue that inserts into the lateral tibia (Gerdy’s Tubercle)
What muscles can you identify?
The Major Knee Ligaments
1. ACL – Anterior Cruciate Ligamentprevents anterior motion of tibia
2. PCL – Posterior Cruciate Ligamentprevents posterior motion of tibia
3. MCL – Medial Collateral Ligament4. LCL – Lateral Collateral Ligament
ACL and PCL run from femur to tibia and form an X inside the knee
The Collateral Ligaments
MCL:- Medial Collateral
Ligament- Runs from
medial femur to medial tibia
LCL:- Lateral Collateral
Ligament- Runs from lateral
femur to head of fibula
The Meniscus
A “c”-shaped piece of fibrocartilage located in the knee joint between the femur and attached to the top of the tibia
Cartilage = meniscus
Differences between medial and lateral Medial
- larger and more C-shaped
- more firmly attached to tibia - has attachments to MCL
Lateral
- smaller and more round or O-shaped- not firmly attached to tibia and LCL
Blood Supply to the Meniscus Mostly avascular – little or no blood
supply Only the outer 20% has a blood
supply* Does not have the ability to heal
itself unless there is a small tear in the outer 20%
Functions of Meniscus
1. Stability2. Shock absorption3. Lubrication and nutrition4. Allows adequate weight distribution
Normal Torn
Total Knee Joint Replacement Surgery to replace a painful
damaged or diseased knee joint with an artificial joint (prosthesis)
Artificial hip invented 1962 1969 – first artificial knee in USA
The Knee Surgery Thin layer of bone removed from
femur – thin metal replaces it Upper layer of tibia replaced with
plastic Back of patella replaced with plastic Parts fastened with “bone cement”
Risks of Knee Joint Replacement Blood clots in large veins Infection Stiffness Implant Loosening/Failure
- more of a problem in younger patients
Knee Injuries and Conditions
Genu Valgum: “knock knees”
Genu Varum: “bowlegs”
Genu Recurvatum:
hyperextension of the knee joint
Patellofemoral Disorders Problems with patella – most common
cause of knee pain Anatomy:
- Patella is a sesamoid bone formed in Quad tendon- Patellofemoral joint – patella and femur- Compression forces –
<body weight during walking2.5 x body weight during stairs
Patellar Tendonitis “Jumper’s Knee” Inflammation and degeneration of
the tendon that connects the kneecap (Patella) to the shin bone (Tibia).
Chondromalacia Damage to the cartilage under the
kneecap Causes: abnormal patellar tracking Most Common Symptom: Knee pain when
walking up and down stairs Prevention: strengthen quads
Minimize squats, downhill running, biking with low seat
Chondromalacia
Patellar Dislocation Involves the
patella sliding out of its position on the knee.
Caused by direct blow or abnormal twisting of the knee
Usually lateral
Osgood-Schlatter Disease
1. Painful swelling over tibial tuberosity(patellar tendon insertion)
2. Usually occurs between 9-13 years of age
3. Pain increases with activity
The Chopat Strap
Iliotibial Band Friction Syndrome Occurs where IT Band rubs over
femur at the knee joint Common in running (esp. downhill)
or any activity with repetitive flexion Hills or stairs increase pain Lots of IT Band stretching
Popliteal Cyst “Baker’s Cyst” Fluid accumulation in posterior knee
(popliteal space) Patient usually complains of a mass
behind the knee
Prepatellar Bursitis “Housemaid’s Kne
e” Tender swelling
over the kneecap (prepatellar bursa)
Pes Anserine Bursitis Inflammation of a bursa in your knee. The
pes anserine bursa is located on the inner side of the knee just below the knee joint.
Tendons of three muscles attach to the shin bone (tibia) over this bursa
SGT: Sartorius, Semitendinosis, Gracilis
Knee Sprains
ACL Sprain >200,000 injuries/year >100,000 reconstructions/year Higher incidence in females Males = contact
Females = noncontact
http://www.youtube.com/watch?v=PzpOEdUdoM4
ACL Sprain1. MOI: twisting of knee
forced hyperextension lateral blow to knee
*foot must be firmly anchored to playing surface
2. 50% of people describe a “pop” in knee 3. Knee fills with blood quickly
Hemarthrosis4. Usually immediate loss of motion5. Knee feels unstablehttp://www.youtube.com/watch?v=uuoj_HFG5Z0&feature=fvst
Anterior Drawer Test:
examiner attempts to slide the tibia forward which may indicate a torn ACL ligament
http://www.youtube.com/watch?v=1iWqUsd1aqY
ACL Sprain Who needs
surgery? - Activity level? - Level of
Competition - Age?
ACL Surgery Arthroscopic Graft options Patellar Tendon
SemitendinosusGracilisCadaverSynthetic
http://www.youtube.com/watch?v=Xsq0sQp6DwUhttp://www.youtube.com/watch?v=dZiDd6e4drc
PCL Sprain
1. MOI: excessive hyperextension hyperflexion
tibia forced posteriorly (blow to front of knee)“dashboard knee”
Possibly 90% of all PCL injuries due to motor vehicle accidents?
2. Mild hemarthrosis3. Posterior knee pain4. Walk with knee
slightly flexed, avoid full extension
5. Posterior sag of tibia6. Surgery?
MCL Sprain MOI: Blow to the outside of the
knee = Valgus Force Possible overuse – breaststroke in swimmers
Commonly associated with meniscal injuries – attached to medial meniscus
No surgery
MCL Sprain
Valgus Stress Test:tests for injury to the MCL ligament
LCL Sprain MOI: Blow to inside of the knee –
Varus force
Grade III tear may require surgery
Varus Stress Test:tests for injury to the LCL ligament
Injuries to the Meniscus
1. MOI: Rotation of the knee as the knee extends during rapid cutting or pivoting
2. Signs and Symptoms:- pain- joint line tenderness- catching or locking- knee buckling or giving way- swelling- incomplete flexion- clicking on stair climbing
3. Surgery?Meniscectomy: removal of the
meniscus- Total meniscectomy =
osteoarthritis
Depends on location of tear, type of tear, and blood supply
Types of Meniscal Tears- bucket handle- Flap tear- Transverse tear- Horn tear
Tests for Meniscal Tears Apley’s
Compression
“The Unhappy Triad” Tear of the medial
meniscus, anterior cruciate ligament (ACL), and medial collateral ligament (MCL)