Aging certainly plays a role in osteoarthritis (OA). As people age, cartilage is normally less able to repair itself. But research has identified some characteristics of OA that usually do not occur in normal aging joints: the water content in cartilage decreases early in the disease process, biochemical changes cause physical and chemical changes, the bone beneath the cartilage is affected, and weight-bearing joints, such as the knee, are more often affected than joints that do not bear weight, such as the elbow. The exact cause of OA is still unknown. A number of factors appear to be involved, including the normal aging process, being overweight or obese, genetic predisposition, muscle weakness, and joint stress and injury. Joint stiffness, especially without joint pain, can be caused by many conditions and often is related to the normal changes of aging. Your doctor can help identify the reason for your joint stiffness and determine appropriate treatment.