MRCS Part B (OSCE) - Online Resources

"The knee joint, the largest synovial joint in the body, is of the modified-hinge variety. "

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The arrangement of the structures within the knee joint from anterior to posterior are as follows:

• Transverse meniscal ligament (stretches across the anterior horns of the medial and lateral menisci).
• Anterior horn of the medial meniscus.
• Anterior cruciate ligament.
• Anterior horn of the lateral meniscus.
• Posterior horn of the lateral meniscus.
• Posterior cruciate ligament.

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The knee joint has three articular surfaces:

• Lateral and medial articulations between the femoral and tibial condyles.
• Intermediate articulation between the patella and femur.

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The attachments of the patella ligament are:

• Superior :      Apex of the patella.
• Inferior :      Tibial tuberosity.

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"The patella ligament extends the knee joint. "

"The knee jerk reflex is elicited on the patella ligament (L3, L4). "

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• The intra-articular ligaments within the knee joint consist of the cruciate ligaments and menisci (semilunar cartilages). The popliteal tendon is also intra-articular during part of its course.

• The extra-articular ligaments of the knee joint are the medial and lateral collateral ligaments.

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"The anterior cruciate ligament attaches to the anterior intercondylar area of the tibia (medial side) and runs upwards, posteriorly and laterally to attach to the medial surface of the lateral femoral condyle. "

The posterior cruciate ligament is attached to the posterior part of the tibial intercondylar area (lateral side) and runs upwards, superiorly and medially to attach on the lateral aspect of the medial femoral condyle

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• The anterior cruciate ligament resists forward displacement of the tibia on the femur and becomes taut in hyperextension of the knee, it also resists rotation.
• The posterior cruciate ligament resists backward displacement of the tibia on the femur and becomes taut in hyperflexion.

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 Anterior draw test and Lachman test : Tests integrity of the ACL.
 Posterior draw test : Tests integrity of the PCL.

 The two menisci of the knee are crescent-shaped fibrocartilages that fill the gap between the tibia and femur.
 The inner edges move freely because they are not attached to the bone. This lets the menisci change shape as the joint moves. The front portion of the meniscus is referred to as the anterior horn, the back portion is the posterior horn, and the middle section is the body.
 The outer margins are fairly thick and well vascularised from the capsule whilst the inner surfaces are thin.
 The poor blood supply to the inner 1/3rd of the meniscus makes it difficult for tears in this part of the meniscus to heal.

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• The medial meniscus is an elongated ""C""- shaped structure (as the tibial surface is larger on the medial side).
• The lateral meniscus is smaller and more circular in shape.
• Medial meniscus is attached to the medial collateral ligament and joint capsule, and therefore less mobile.
• The lateral meniscus however, has no attachment to the lateral collateral ligament or joint capsule therefore is more mobile.
• Popliteus tendon runs between the joint capsule and the lateral meniscus

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The medial meniscus has a strong attachment to the medial collateral ligament so is much less mobile than the lateral meniscus and therefore can’t accommodate abnormal stresses as easily.

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The menisci:

• Act as ‘shock absorbers’
• Help to distribute the load by increasing the congruity of the articulation.
• Contribute to joint stability.
• Assist in proprioception.
• Lubricate the knee joint.

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• Suprapatellar bursa: Lies between the infero-anterior surface of the femur and the deep surface of quadriceps femoris.
• Pre- patellar bursa: Between the patella and the skin.
• Superficial and deep infrapatellar bursae: Lie between the patellar ligament and skin and the tibia and patellar ligament.

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The radiological features of osteoarthritis are:

• Loss of joint space.
• Subchondral sclerosis.
• Osteophytes.
• Subchondral cysts.

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