Osteoarthritis is a type of degenerative arthritis that occurs when the cartilage that acts as padding between the joints breaks down. Osteoarthritis is characterized by pain, swelling, and stiffness in the joint that is worse after periods of inactivity. As the disease progresses, patients may notice an enlargement of the affected joints and increasing loss of mobility. Osteoarthritis is largely a disease of aging, resulting from regular use or overuse of the main weight-bearing joints of the body, especially the hips and knees. Treatment for osteoarthritis is mainly conservative, consisting of a combination of physical therapy for exercise and medication to control pain. In late stage disease, surgery including joint replacement is also a possibility.