Osteoarthritis

Osteoarthritis, the most common form of arthritis, accounts for more than 85 percent of arthritis cases. Osteoarthritis is a degenerative disease that affects the hip, knee, back, and hand joints, as well as others. The causes of osteoarthritis are numerous and can include trauma or infection, but often no cause is identifiable. Mechanical stress, combined with abnormal biomechanics, leads to the initial damage to the joint cartilage, which then starts to break down. Immobilization of a joint, such as being in a cast, can also lead to degenerative articular cartilage changes. Repetitive loading and unloading of the joint forces fluid into and out of the joint, getting nutrition to the articular cartilage. When a joint is immobilized, these compressive forces are absent. As damage to the articular cartilage progresses, the joint space lessens and the bone underlying the cartilage experiences abnormal stresses and deforms.

Doctors diagnose osteoarthritis by correlating a patient's history and physical examination to his or her x-ray and laboratory test results. The amount of joint damage is only predictive of severity of symptoms for a small part of the population, however. Risk factors include female gender, obesity, joint injury, occupation, and smoking.

Osteoarthritis symptoms can develop slowly or rapidly, depending on the cause of the arthritis, presence of other diseases, activity level, and other influences. For the majority of individuals, however, development of symptoms is gradual and slow. The most common complaint is aching within a joint, accompanied by stiffness after sitting for prolonged periods. This stiffness generally lasts less than 30 minutes and is resolved with gentle movement. Many patients report grating with movement of the involved joint, and as the disease progresses, the joint may become deformed and lose motion. As osteoarthritis results from articular cartilage damage, it may be limited to only one joint and, as noted earlier, occurs largely in the weight-bearing joints.