The knee is the largest joint in your body and subject to enormous stress. To help distribute this stress and stabilize this joint, the body has semicircular shaped rims of fibrocartilage along the inside and outside of the knee. These structures are called the menisci (plural) or meniscus (singular). The one on the inside of the knee is call the medial meniscus and the one on the outside the lateral meniscus.
When we pivot on the knee, a shear force can occur that causes the meniscus to tear. Tears in younger people usually require a significant force. As we age, our menisci weakens and become thin making them more susceptible to tear. Meniscus tears in older people are often called degenerative tears. When someone says they have a torn cartilage, what they mean is that they have a torn meniscus.
The most common symptom of a meniscus tear is pain, which is usually aggravated by activity. People will also frequently experience swelling, catching and locking of the joint. Sometimes the knee will feel like it is giving away. Meniscus tears are most commonly diagnosed by examination, MRI scan, and arthroscopic surgery.
Meniscus injuries are usually treated arthroscopically. The peripheral portion of the meniscus, that is the part furthest from the center of the joint, usually has a good blood supply and can sometimes be surgically repaired. However, the central 2/3 of the meniscus, does not have blood vessels and receives its nutrition from the synovial fluid of the joint. These central tears do not heal if sewn and are best treated by surgical removal of the torn component. When removing a torn meniscus, the surgeon attempts to preserve as much of the normal meniscus as possible.
After treatment for a meniscus tear, most people resume full activities without knee pain. Those who were active in sports prior to the tear, usually remain active in sports after surgery. If a person has other associated problems with the knee, such as arthritis, symptoms may persist from that condition.