Arthritis is the name for a set of conditions that cause inflammation in the joints. Osteoarthritis (OA) occurs when the cartilage that normally cushions the ends of the bones in your joints gets worn away and the bones begin to rub against each other (“osteo” means bone). OA, also called degenerative joint disease or osteoarthrosis, is by far the most common form of arthritis.

OA usually affects only one joint in your body, although it can affect more. The most commonly affected joints are your hands, hips, knees, and spine, but OA can affect any joint. Another type of arthritis called rheumatoid arthritis tends to affect several joints at once. OA tends to get worse with time and there is no cure for the condition. However, there are treatments that can help manage the pain and loss of mobility that often accompany the disease.

An estimated 12 percent of the U.S. population (nearly 21 million Americans) has OA. The disease gets more common as people get older and occurs most frequently in people who are overweight and those whose jobs or lifestyles place a lot of stress on particular joints. Younger people can develop OA too, but it is often due to a joint injury, abnormal joint anatomy, or a genetic defect in joint cartilage.