Rheumatoid Arthritis

About

Less common than osteoarthritis, rheumatoid arthritis (RA) affects 1 percent to 2 percent of the population (about 2.1 million people) and three times more women than men. The disease strikes multiple joints as well as other tissues and organs throughout the body. Although symptoms begin most often between ages 20 and 40, RA may develop at any age.

RA is an autoimmune disorder. Such disorders result when the body initiates an immune response against some natural body constituent mistakenly recognized as foreign. The joint damage caused by RA begins with inflammation of the connective tissue lining the cavity of a joint, or synovial membrane. The inflammation leads to a thickening of this membrane due to overgrowth of synovial cells and accumulation of white blood cells. Release of enzymes and growth factors by the white blood cells, along with continuing growth of the synovial membrane, can erode cartilage as well as bones, tendons, and ligaments within the joint capsule. As RA progresses, the production of excess tissue can further limit joint motion. Inflammation of tissues surrounding the joint also contributes to joint damage.

People with rheumatoid arthritis can deal with their condition by learning as much as possible about its causes, effects, and treatments. A greater knowledge of arthritis makes it easier to anticipate and deal with the fluctuations in its course and find ways to overcome the physical limitations it may cause.

This section has more on:

• Need-to-know anatomy
• Causes and risk factors

Need-to-know anatomy

A joint is where two or more bones meet, or "articulate." The ends of the bones are covered by the articular cartilage, a tough but slippery material that cushions the joint and allows the bones to move smoothly. Although the word cartilage usually refers to articular cartilage, there is a second type of cartilage called meniscal cartilage that adds an extra layer of shock absorption to the knee in the form of two crescent-shaped pads.

The joint is sealed within a joint capsule. The outside of the joint capsule is formed by ligaments, which attach bones to other bones, and tendons, which attach muscle to bone. The synovial membrane--a thin, delicate covering on the inside of the joint capsule--secretes synovial fluid, which fills the inside of the capsule and serves as a lubricant for joint movement.

Causes and risk factors

The exact cause of RA is unknown. Genetics play some role, since certain people inherit a susceptibility to the disease. There may also be an environmental factor that triggers RA, such as a virus or bacterium.

Several studies have found that heavy smokers are more likely to develop RA than nonsmokers. Some studies have suggested that drinking coffee might increase the risk of RA and drinking tea might decrease the risk, but a 2003 review of data on more than 80,000 women over a period of nearly 20 years concluded that neither beverage affects RA risk.