One of the most commonly injured parts of the knee is the meniscus, a wedge-like rubbery cushion where the major bones of your leg connect. Meniscal cartilage curves like the letter "C" at the inside and outside of each knee. A strong stabilizing tissue, the meniscus helps the knee joint carry weight, glide and turn in many directions. It also keeps your femur (thighbone) and tibia (shinbone) from grinding against each other.

Causes
Football players and others in contact sports may tear the meniscus by twisting the knee, pivoting, cutting or decelerating. In athletes, meniscal tears often occur in combination with other injuries such as a torn ACL (anterior cruciate ligament). Older people can injure the meniscus without any trauma as the cartilage weakens and wears thin over time, setting the stage for a degenerative tear.

Menisci tear in a number of different ways. Young athletes often incur longitudinal or "bucket handle" tears if the femur and tibia trap the meniscus when the knee turns. Less commonly, young athletes can develop a combination of tears called radial or "parrot beak" in which the meniscus splits in two directions due to repetitive stress activities such as running. In older people, cartilage degeneration that starts at the inner edge causes a horizontal tear as it works its way back.

Symptoms
You might experience a "popping" sensation when you tear the meniscus. Most people can still walk on the injured knee and many athletes keep playing. When symptoms of inflammation set in, your knee feels painful and tight. You may feel stiffness and swelling, tenderness in the joint line, or develop a collection of fluid ("water on the knee"). Without treatment, a fragment of the meniscus may loosen and drift into the joint, causing it to slip, pop or lock-your knee gets stuck, often at a 45-degree angle, until you manually move or otherwise manipulate it. If you think you have a meniscal tear, see your doctor right away for diagnosis and individualized treatment.

Treatment
Initial treatment of a meniscal tear follows the basic RICE formula: rest, ice, compression and elevation, combined with nonsteroidal anti-inflammatory medications for pain. If your knee is stable and does not lock, this conservative treatment may be all you need. Blood vessels feed the outer edges of the meniscus, giving it the potential to heal on its own. Small tears on the outer edges often heal themselves with rest.

Surgical Options
If your meniscal tear does not heal on its own and your knee becomes painful, stiff or locked, you may need surgical repair. Depending upon the type of tear, whether you also have an injured ACL, your age and other factors, your doctor may use an arthroscope to trim off damaged pieces of cartilage. A cast or brace immobilizes your knee after surgery. You must complete a course of rehabilitation exercises before gradually resuming your activity.