In the knee there are two ring cartilages called menisci. There is one on the inside (medial) side of the knee and one on the outside (lateral) side of the knee. The menisci act primarily as shock absorbers and provide some stability in the knee.
Tears of the menisci are very common, with the medial meniscus being torn more commonly than the lateral meniscus. Tears often happen during a twisting injury or fall.
Sometimes tears are degenerative and not due to an acute injury. The torn meniscus can get caught up in the joint, causing pain or sometimes blocking the knee from moving.
Meniscus tears are usually treated by arthroscopy (keyhole surgery). The meniscus does not have a blood supply and therefore is not able to heal. For this reason, only a very small percentage of meniscus tears can be repaired.
In most cases, the torn section of the meniscus is removed, leaving as much healthy meniscus behind as possible.