Knee meniscus

The articulating articular surfaces of the tibia do not correspond to those of the femur. In order to maintain uniform pressure distribution per unit area within the appropriate limits, such anatomical formations as menisci are present. The meniscus of the knee joint is a semicircular connective tissue strand occupying the space between the tibia and femur. The contact area of the articulating surfaces in the joint is small, the menisci significantly increase it. They are capable of deforming during movements, which allows the tibia to change the shape of the articular surface in full accordance with the change in the surface of the femur.

A careful study of the shape of the menisci led anatomists to the conclusion that their beveled surface not only acts as a barrier to prevent the tibia from shifting, but also helps distribute the vertical load on it tangentially, which significantly reduces the stress impact during extreme movements (jumping, running, etc.).

The meniscus of the knee joint is tightly attached to the tibia. When flexed, they shift posteriorly. The mobility of the menisci allows them to move in the anteroposterior direction independently of each other during internal and external rotation of the tibia. The medial meniscus of the knee joint has a tighter attachment to the capsule than the lateral one. In this regard, many authors note a higher frequency of tears of the medial meniscus. It is most rigidly attached at the site of origin of the posterior oblique ligament. The meniscus of the knee joint is mainly avascular. Only their peripheral part is vascularized. The avascular zone of the meniscus is nourished by alternating compression and decompression of the meniscus cartilage during cyclic movements. This leaves the central part of the meniscus avascular and free from articulation, but it is this area that is predisposed to degenerative changes.

Half of the compression load on the knee joint. B is transmitted through the menisci during extension and 85%, respectively, at 90° flexion in the joint. After its removal, the contact area of the femur and tibia decreases by 50%. Even partial meniscectomy leads to a significant increase in pressure per unit area.

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Types of meniscus of the knee joint

Discoid meniscus of the knee joint is the most common form of meniscus in the lateral compartment of the joint. Its frequency is from 2 to 15%. In this situation, the lateral meniscus covers almost the entire outer part of the tibia. There are three types of this meniscus. The first two - complete and incomplete - are the usual variants of the structure. The peripheral attachment in these cases is standard. The third type is called the "Wrisberg ligament type", where a shortened Wrisberg ligament attaches the meniscus to the medial femoral condyle, thereby causing it to shift posteriorly during full extension in the joint. The first two types of meniscus are normal variants, although they predispose to degenerative changes and ruptures, especially in the older age group. The third type - often makes itself known in the early years of life, clinically it is manifested as a "clicking" joint. There are some characteristic radiographic changes that accompany discoid meniscus of the knee joint: flattening of the lateral condyle of the femur, widening of the outer part of the joint space, cup-shaped concavity of the lateral part of the tibia, high position of the head of the fibula, flattening of the outer tubercle of the intercondylar eminence.