What Is It?

Rheumatoid arthritis is a chronic (long-lasting) inflammatory disease that causes pain, stiffness, warmth, redness and swelling in joints. Over time, the affected joint can become misshapen, misaligned and damaged. Tissue lining the joint can become thick, and may wear away surrounding ligaments, cartilage and bone as it spreads. Rheumatoid arthritis usually occurs in a symmetrical pattern, meaning that if one knee or hand has it, the other usually does, too.

The cause of rheumatoid arthritis is unknown, although it appears to be a disease of the autoimmune system. When the body's immune system does not operate as it should, white blood cells that normally attack bacteria or viruses attack healthy tissue instead - in this case, the synovium, or joint tissue. As the synovial membrane (the thin layer of cells lining the joint) becomes inflamed, enzymes are released. Over time, these enzymes eat away at cartilage, bone, tendons and ligaments near the joint.

Some research suggests that a virus triggers this faulty immune response. However, there is not yet convincing evidence that a single virus is the cause in all patients. At the same time, it appears that some people are more likely to get the disease because of their genetics.

Rheumatoid arthritis, the most disabling form of arthritis, generally affects more than one joint at a time. Commonly affected joints include those in the hands, wrists, feet, ankles, elbows, shoulders, hips, knees and neck. Rheumatoid arthritis can result in loose, deformed joints, loss of mobility and diminished strength. It also can cause painless lumps the size of a pea or acorn, called rheumatoid nodules. These develop under the skin, especially around the elbow or beneath the toes.

Generally, the pain of rheumatoid arthritis is described as a dull ache, similar to that of a headache or toothache. Pain is typically worse in the morning. It is not rare to have 30 minutes to an hour or more of morning stiffness. On days when the disease is more active, you may experience fatigue, loss of appetite, low-grade fever, sweats and difficulty sleeping.