The meniscus is a semicircle of cartilage within the knee joint that acts like a cushion between the femur (thigh bone) and the tibia (shin bone). Two menisci (lateral and medial) are present in each knee. Meniscal tears result result from injuries and are much more common in adults than children. They affect the medial meniscus more commonly than the lateral.
Sometimes babies are born with a complete disc of cartilage rather than a semicircle (discoid meniscus). The lateral meniscus is almost always affected and in many cases both knees are involved. Patients will frequently complain of giving way or popping and sometimes they can demonstrate a visible clunking over the lateral joint line. The diagnosis is easily confirmed with MRI scans.