Disc meniscus

Definition

A disc meniscus is an anatomical variant of a meniscus in the knee joint. The two menisci in the knee are cartilage discs that serve to align the joint surfaces of the thigh bone and lower leg bone, which do not fit exactly on top of each other. Normally, these menisci are approximately crescent-shaped.

One speaks of a disc meniscus if one of these menisci instead has a disc shape and is larger than usual. Therefore, a disc meniscus reaches up to the edge of the tibia bone. In almost 95% of the cases the change of shape affects the outer meniscus. In about every fifth patient, both knees are affected.

Frequency

Since a disc meniscus usually causes symptoms late or not at all, it is difficult to determine how many people have this anatomical variant. However, it is assumed that between 0.4 and 17% are affected. It is noticeable that people in Asia, especially Japan, have a disc meniscus much more often than inhabitants of western countries.

Cause

The reason why some people have a disc meniscus has not yet been finally clarified. It is assumed, however, that this form deviation is not already congenital, but is caused by certain incorrect loads on the knee joint.

Symptoms of a disc meniscus

Often a disc meniscus causes no discomfort at all. The first symptom often occurs between the ages of six and eight. This is because, due to size and weight, this is the age at which the disc meniscus typically first becomes wedged between the tibial plateau and the femoral condyle when the knee is loaded.

If such an entrapment is not detected or not treated, arthrosis can develop at this point in the further course of the disease. If it is moved in this way, a snapping occurs, which becomes noticeable when the joint moves. Occasionally this snapping phenomenon is accompanied by pain, which is classically located on the outside of the knee. Otherwise, disc meniscus patients only experience pain when the meniscus is injured (especially meniscus tear or detachment from the holding apparatus of the meniscus). These injuries are then accompanied by the typical symptoms, i.e. in particular pain and restricted mobility.