What causes osteoarthritis?

In OA, biochemical and metabolic changes in the body result in the breakdown of joint cartilage. Over time, the joint cartilage wears away and bony growths (osteophytes) may form at the edges of joints. The cartilage loses its ability to effectively cushion the area between the two bones, and osteophytes may press on surrounding tissue. This results in pain that may range from mild to disabling.