Osteoarthritis is the degeneration of the joint—a disease process causing the joint surface to wear away. The symptoms can include all or some of the following: pain, stiffness, swelling, warmth, loss of motion, decreased activity, tenderness and crepitus (grinding). Causes of osteoarthritis include age, sex, obesity, genetic disposition, bone deformities, certain metabolic diseases, previous injury or surgery and repetitive high-impact activities.