Knee joint Flashcards
Which joints are found in the knee joint?
Tibiofemoral joint
Patellofemoral joint
What type of joint is the knee joint?
Synovial
Modified hinge
Which movements occur at the knee joint?
Flexion/extension
Slight rotation in flexion
When is the knee joint most stable?
Why?
Extension (close packed position)
Strong support from ligaments
Whta type of bone is the patella?
Sesamoid - resides within quadriceps tendon
What is the patellofemoral joint enclosed by?
Same capsule that encloses tibiofemoral joint
Describe why the articular surfaces provide little support in the knee joint?
Discrepancy in shape: distal end of femur has rounded condyles, which articulate with a flat tibial plateau
Where does the knee joint gain most of its support from?
Cruciate ligaments
Collateral ligaments
Menisci
When is the knee joint most susceptible to injury?
In flexion and rotation
Describe the articular surfaces of the knee joint?
Medial condyles of femur and tibia longer than lateral
Lateral condyles of femur and tibia wider than medial
Inter-condylar area
What is the significance of the inter-condylar notch of the femur?
Contains ACL
What is the significance of the inter-condylar area of the tibia?
Site of attachment of menisci and cruciate ligaments
Describe the changes that occur in the knee joint during extension?
Femur rotates medially on fixed tibia
Occurs in last 15-20 degrees
All ligaments tight in full extension
PASSIVE
Describe the changes that occur in the knee joint during flexion?
ACTIVE contraction of politeus
Femur rotates laterally on fixed tibia
Describe the direction of pull of politeus?
Describe the capsule of the knee joint?
Attached around articular margins
Encloses intracapsular structures: menisci, cruciate ligaments, synovial membrane
Describe the location of the cruciate ligaments in relation to the joint capsule and synovial membrane?
Intracapsular
Extrasynovial
Describe the reinforcements of the joint capsule?
Anterior: patellar tendon and retinacular fibres
Lateral: popliteus, biceps femoris, iliotibial tract
Medial: pes anserinus tendons
Posterior: oblique popliteal ligament (from semimembranosus)
Describe the pes anserinus at the knee joint?
Muscle insertions: sartorius, gracilis, bursa, semitendinosus
(SAY GRACE BEFORE TEA)
Describe the deficiencies in the capsule of the knee joint?
Above: suprapatellaer bursa
Posteriorly: politeus tendon and semimembranosus bursa
Where in the knee joint does a Baker’s cyst arise?
Posteriorly
Swelling of semimembranosus bursa
List the bursae of the knee joint?
Which are communicating?
COMMUNICATING
Suprapatellar
Popliteus/semimembranosus
NON-COMMUNICATING
Prepatellar
Superficial infrapatellar
Deep infrapatellar
Describe the attachments of the cruciate ligaments?
ACL: attaches anteriorly on the tibia, and lateral condyle of the femur
PCL: attaches posteriorly on the tibia, and medial condyle of the femur
What are the functions of the cruciate ligaments?
Prime stabilisers in the AP direction
ACL: prevents tibia being displaced anteriorly to femur, or femur being displaced posterior to tibia when weight bearing
PCL: prevents tibia from being displaced posteriorly to femur, or femur being displaced anterior to tibia when weight bearing
Describe the changes that occur in the ACL during joint felxion and extension?
Ligament twists on itself during flexion
Untwists in extension and pulls lateral condyle in medial direction (passive extension)
When does injury of the ACL occur?
When rotation occurs laterally
Involves extension on weight-bearing leg
When is the PCL prone to injury?
Fall on flexed knee
Bumper bar impact
Describe the attachments of the MCL?
Medial epicondyle of femur
Superifical: medial tibia
Deep: blends with deep fibres of medial meniscus
Describe the structure of the MCL?
2 parts: superficial (long, broad fibres) and deep (merges with medial meniscus) fibres
Describe the function of the MCL?
Resists valgus forces
Resists lateral rotation of tibia
Limits anterior displacement of tibia when ACL damaged
Describe the attachments of the LCL?
Lateral epicondyle of femur
Lateral tibia
What separates the LCL from the lateral meniscus?
Popliteus
Describe the function of the LCL?
Resists varus forces
Describe the function of the menisci?
Shock absorb
Weight distribution
Increase area of contact in knee joint by 1/3
Describe the structure of the menisci?
Fibrocartilage
Wedge-shaped
Which meniscus is more commonly injured?
Why?
Medial: longer, horns are further apart, less mobile (MCL attachment)
Describe the consequence of meniscal injury?
Contributes to locked knee
Describe the repair of meniscal tears?
Tear in periphery - can be reapired due to blood supply
Tear in centre - poor repair due to poor blood supply
What are the articular surfaces in the patello-femoral joint?
Patella
Patellar surface of femur
Which structures maintain the alignment of the patello-femoral joint?
Vastus medialis
Medial patellar retinaculum
Raised lip on lateral femoral condyle
Why is the patella prone to tracking laterally?
Pulled by strong quadriceps muscles
What does lateral tracking of ther patella predispose to?
Subluxation/dislocation
What is Angle Q?
Quadriceps angle
Angle between tendon of quadriceps and patellar tendon
