The knee contains two pads of cartilage (menisci) that act as shock absorbers between the femur (thigh bone) and tibia (shinbone). Tearing of the cartilage (a meniscus tear) usually occurs as a result of a sudden twisting of the leg; it is a common sports injury.
Symptoms typically include sudden pain in the knee, swelling of the knee, and difficulty straightening the leg.
A mild tear may be treated with rest and nonsteroidal anti-inflammatory drugs.
A severe tear may require surgery to repair or remove the damaged cartilage.