Knee joint Flashcards by Brooke Ward

Which joints are found in the knee joint?

Tibiofemoral joint

Patellofemoral joint

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What type of joint is the knee joint?

Synovial

Modified hinge

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Which movements occur at the knee joint?

Flexion/extension

Slight rotation in flexion

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When is the knee joint most stable?

Why?

Extension (close packed position)

Strong support from ligaments

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Whta type of bone is the patella?

Sesamoid - resides within quadriceps tendon

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What is the patellofemoral joint enclosed by?

Same capsule that encloses tibiofemoral joint

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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

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Where does the knee joint gain most of its support from?

Cruciate ligaments

Collateral ligaments

Menisci

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When is the knee joint most susceptible to injury?

In flexion and rotation

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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

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What is the significance of the inter-condylar notch of the femur?

Contains ACL

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What is the significance of the inter-condylar area of the tibia?

Site of attachment of menisci and cruciate ligaments

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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

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Describe the changes that occur in the knee joint during flexion?

ACTIVE contraction of politeus

Femur rotates laterally on fixed tibia

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Describe the direction of pull of politeus?

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Describe the capsule of the knee joint?

Attached around articular margins

Encloses intracapsular structures: menisci, cruciate ligaments, synovial membrane

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Describe the location of the cruciate ligaments in relation to the joint capsule and synovial membrane?

Intracapsular

Extrasynovial

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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