Osteoarthritis (OA) is the most common joint disorder.

Most of the time, the cause of OA is unknown. It is mainly related to aging, but metabolic, genetic, chemical, and mechanical factors can also lead to OA.

The symptoms of osteoarthritis usually appear in middle age and almost everyone has them by age 70. Before age 55, the condition occurs equally in both sexes. However, after 55 it is more common in women.

The disease causes the cushioning (cartilage) between the bone joints to wear away, leading to pain and stiffness. As the disease gets worse, the cartilage disappears and the bone rubs on bone. Bony spurs usually form around the joint.

OA can be primary or secondary.

Primary OA occurs without any type of injury or obvious cause.

Secondary OA is osteoarthritis due to another disease or condition. The most common causes of secondary OA are metabolic conditions, such as acromegaly, problems with anatomy (for example, being bow-legged), injury, or inflammatory disorders such as septic arthritis.

The symptoms of osteoarthritis include:

• Deep aching joint pain that gets worse after exercise or putting weight on it and is relieved by rest
• Grating of the joint with motion
• Joint pain in rainy weather
• Joint swelling
• Limited movement
• Morning stiffness

Some people might not have symptoms.

A physical exam can show limited range of motion, grating of a joint with motion, joint swelling, and tenderness.

An x-ray of affected joints will show loss of the joint space, and in advanced cases, wearing down of the ends of the bone and bone spurs.