Osteoarthritis (OA) is a common disorder that affects the joints and is caused by a loss of cartilage. Cartilage is the covering over the ends of bones that serve to provide a smooth gliding surface. When this cartilage surface is lost or destroyed, the underlying bone becomes exposed. As the disease progresses, more cartilage is lost and eventually bone rubs against bone within the joint. The disease is generally progressive and often results in pain, deformity, and stiffness. These problems can have a major impact on your quality of life and activity level. Osteoarthritis affects over 27 million individuals in the United States alone.