Osteoarthritis , or degenerative joint disease, refers to the pain and swelling that can result from the progressive loss of cartilage in the joints. It is the most common form of arthritis, affecting nearly 27 million adults in the United States, particularly older adults. In osteoarthritis, the protective cartilage that cushions the ends of bones within joints gradually wears away, which is why it is sometimes called "wear and tear" arthritis. It can affect almost any joint in the body, but commonly involves the weight-bearing joints: the knees, hips, and spine. It can also affect the fingers and any joint with previous injury from trauma, infection, or inflammation. The inner bone surfaces become exposed and rub together, and in some cases, bony spurs develop on the edges of joints, causing damage to muscles and nerves, pain, deformity, and difficulty moving.
Although the mechanism behind osteoarthritis is unknown, some people appear to have a genetic predisposition to degenerative joint disorders. This is often the case for people who develop it at an early age. Other causes of osteoarthritis include:
Misuse of anabolic steroids (used by some athletes).
Trauma to joint surfaces.
Being overweight, which can cause early and more rapid progression of joint problems, especially in the knee.