Definition of Osteoarthritis:

Osteoarthritis (OA) is the most common joint disorder.

Causes, incidence, and risk factors:

Osteoarthritis is caused by 'wear and tear' on a joint.

• Cartilage is the firm, rubbery tissue that cushions your bones at the joints, and allows bones to glide over one another.
• Cartilage can break down and wear away. As a result, the bones rub together, causing pain, swelling, and stiffness.
• Bony spurs or extra bone may form around the joint, and the ligaments and muscles around the hip become weaker and stiffer.

Often, the cause of OA is unknown. It is mainly related to aging. The symptoms of OA usually appear in middle age. Almost everyone has some symptoms by age 70. However, these symptoms may be minor. Before age 55, OA occurs equally in men and women. After age 55, it is more common in women.

Other factors can also lead to OA.

• OA tends to run in families
• Being overweight increases the risk of OA in the hip, knee, ankle, and foot joints
• Fractures or other joint injuries can lead to OA later in life
• Long-term overuse at work or in sports can lead to OA

Medical conditions that can lead to OA include:

• Bleeding disorders that cause bleeding in the joint, such as hemophilia
• Disorders that block the blood supply near a joint can lead to avascular necrosis
• Other types of arthritis, such as chronic gout, pseudogout, or rheumatoid arthritis