Definition of Arthritis:

Arthritis is inflammation of one or more joints. A joint is the area where two bones meet. There are over 100 different types of arthritis.

See also: Joint pain

Causes, incidence, and risk factors:

Arthritis involves the breakdown of cartilage. Cartilage normally protects a joint, allowing it to move smoothly. Cartilage also absorbs shock when pressure is placed on the joint, such as when you walk. Without the normal amount of cartilage, the bones rub together, causing pain, swelling (inflammation), and stiffness.

Joint inflammation may result from:

• An autoimmune disease (the body's immune system mistakenly attacks healthy tissue)
• Broken bone
• General "wear and tear" on joints
• Infection, usually by bacteria or virus

Usually the joint inflammation goes away after the cause goes away or is treated. Sometimes it does not. When this happens, you have chronic arthritis. Arthritis may occur in men or women. Osteoarthritis is the most common type. See: Osteoarthritis

Other, more common types of arthritis include:

• Ankylosing spondylitis
• Gonococcal arthritis
• Gout
• Juvenile rheumatoid arthritis (in children)
• Other bacterial infections (nongonococcal bacterial arthritis)
• Psoriatic arthritis
• Reactive arthritis (Reiter syndrome)
• Rheumatoid arthritis (in adults)
• Scleroderma
• Systemic lupus erythematosus (SLE)