Test your knowledge: femoral condyles.
The knee joint seems only a simple articulation: motions between femur and tibia are mainly confined to flexion and extension. Nevertheless, there is something unique in the contour and shape of the medial and lateral femoral condyles and their corresponding menisci. Below you find 6 hypotheses regarding the anatomy and arthrokinematics of the knee joint. Which of these hypotheses are correct?
A. The medial condyle is more massive than his lateral counterpart;
B. The lateral condyle has a smaller posteroanterior diameter;
C. The lateral meniscus is smaller than the medial meniscus and has an "O"-formed shape;
D. The medial meniscus is interconnected with the popliteal muscle;
E. The popliteal muscle unlocks end range rotation of the knee joint when extending;
F. The lateral meniscus is more mobile than the medial meniscus and because of that it has a higher rupture prevalence.
The medial condyle is more massive and has a more convex shape. Corresponding to this, the medial meniscus is larger and thicker than the lateral meniscus. The lateral condyle has a higher posteroanterior diameter but is more flattened than its medial counterpart. You would think that the lateral meniscus is reciprocally formed, but it isn’t: the lateral meniscus is more mobile and moves with the rotation of the knee. Because of its mobility, the lateral meniscus is a more common cause for friction and stress in the knee joint than the medial meniscus – which DOES have a higher prevalence of ruptures.
Due to the shape of the condyles and the menisci, and the location of ligaments of and muscles acting on the knee, the joint rotation axis is located medially in the knee joint. This also in part explains why the lateral condyle and meniscus are more mobile. Maximum extension of the knee is caused by these factors and the “screw home” mechanism of the cruciate ligaments. The popliteal muscle is connected with the lateral meniscus and the caput fibulae: it locks the knee joint in and unlocks the knee joint out of its maximum extension. Moreover, it plays an important role for proprioception in the knee joint and is known to cause posterolateral knee pain.
The correct hypotheses were: A and C.