Definition of Osteoarthritis:

Osteoarthritis (OA) is the most common joint disorder.

Causes, incidence, and risk factors:

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. 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:

• Inflammatory disorders such as septic arthritis
• Injury
• Metabolic conditions, such as acromegaly
• Problems with anatomy (for example, being bow-legged)