Menisci

Meniscus we call a half moon or rarely disc-shaped intercartilage of collagen fibres, which occurs in a large number of joints of the body, for example in the knee joint.

The task of the meniscus is to improve the guidance and contact of the joint surfaces (articular cartilage), for example from thigh to lower leg, it also contributes through its height to the tightening of the ligaments and thus to the improvement of lateral ligament strength and buffers the joint surfaces against impacts.

https://en.wikipedia.org/wiki/Meniscus_(anatomy)