Osteoarthritis, also known as degenerative joint disease or osteoarthrosis, is a joint disease that is especially common in older people. More than 20 million Americans are affected by osteoarthritis. In a person who has osteoarthritis, cartilage has worn away, which allows bones to rub together. Common symptoms of osteoarthritis can include joint pain and limited movement. The most common locations for osteoarthritis are the hands, neck, lower back, and the large weight-bearing joints of the body (such as the knees and hips). Treating osteoarthritis can involve exercise, medicines, surgery, or alternative therapies.