Osteoarthritis (OA), which is also known as osteoarthrosis or degenerative joint disease (DJD), is a progressive disorder of the joints caused by a gradual loss of cartilage and resulting in the development of bony spurs and cysts at the margins of the joints.
Osteoarthritis results from deterioration or loss of the cartilage that acts as a protective cushion between bones, particularly in weight-bearing joints such as the knees and hips. As the cartilage is worn away, the bone forms spurs (areas of abnormal hardening), and fluid-filled pockets in the marrow known as subchondral cysts. As the disorder progresses, pain results from deformation of the bones and fluid accumulation in the joints. The pain is relieved by rest and made worse by moving the joint or placing weight on it.
In early OA, the pain is minor and may take the form of mild stiffness in the morning. In later stages of OA, inflammation develops; the patient may experience pain even when the join is not being used; and he or she may suffer permanent loss of the normal range of motion in that joint.