Medial meniscus

Recommended video: Knee joint [29:49]

Sagittal view of the knee joint showing the patellofemoral and tibiofemoral joints.

The medial meniscus is a crescentic, almost semi-circular shaped fibrocartilage disc found on the tibial plateau within the knee joint. Its proximal surface is concave and articulates with the convex-shaped femoral condyles, whilst the distal surface is flat and sitting on the articular cartilage of the tibia, covering almost two thirds of its surface. The medial meniscus is broader posteriorly, with its anterior horn attached to the intercondylar area anterior to the anterior cruciate ligament, while the posterior horn is attached anterior to the posterior cruciate ligament. It is also firmly attached to the fibrous capsule as well as the deep surface of the tibial collateral ligament. These attachments result in the medial meniscus being relatively fixed and have far less movement than the lateral meniscus.

The peripheral border is thicker and better vascularized, whilst the inner border is thinner and less vascular. The inner two-thirds consist of radially organized bundles of collagen, whilst the peripheral one-third consists of circumferentially arranged bundles, suggesting the inner section is more suited to resisting compressive forces, while the periphery is more is better at resisting tensional forces.

Overall, just like the lateral meniscus, the medical meniscus functions to widen and deepen the articular surface of the tibia to improve congruity with the femoral condyles. The improved congruity of the articulation helps to spread the load placed upon the joint and cushion the underlying bones, protecting against damage to the knee joint.