OA is the most common joint disorder. It typically affects the joints of the hands (especially those involved with a pinch-grip), weight-bearing joints (hips, knees and big toes) and the spine.
In normal joints, a rubbery material called cartilage covers the ends of each bone. It provides a smooth, gliding surface for joint motion and acts as a cushion between the bones. In OA, the cartilage wears away leading to joint damage.
The cause of OA is unclear.