One of the most common causes of joint pain is arthritis. The most common types of arthritis are: Osteoarthritis, Rheumatoid Arthritis, Post-traumatic Arthritis, and Avascular Necrosis. Osteoarthritis is sometimes called degenerative arthritis because it is a "wearing out" condition involving the breakdown of cartilage in the joints. When cartilage wears away, the bones rub against each other, causing pain and stiffness. OA usually occurs in people aged 50 years and older, and frequently in individuals with a family history of osteoarthritis.