Rheumatoid arthritis is a destructive joint disease that is caused by inflammation in the tissue that normally produces lubrication fluid for joints. When this tissue remains inflamed, it leads to deformity by loosening joint ligaments and to joint destruction by eroding away cartilage and bone.

Osteoarthritis is a noninflammatory joint disease whereby the cartilage of the joint thins, typically asymmetrically -- so only one knee or hand may be affected. The illustration on the previous page demonstrates the difference between a normal joint and those of osteoarthritis and rheumatoid arthritis.

While rheumatoid arthritis is a chronic illness, meaning it can last for years, patients may experience long periods without symptoms. However, rheumatoid arthritis is typically a progressive illness that has the potential to cause significant joint destruction and functional disability.

A joint is where two bones meet to allow movement of body parts. Arthritis means joint inflammation. The joint inflammation of rheumatoid arthritis causes swelling, pain, stiffness, and redness in the joints. The inflammation of rheumatoid disease can also occur in tissues around the joints, such as the tendons, ligaments, and muscles.

In some people with rheumatoid arthritis, chronic inflammation leads to the destruction of the cartilage, bone, and ligaments, causing deformity of the joints. Damage to the joints can occur early in the disease and be progressive. Moreover, studies have shown that the progressive damage to the joints does not necessarily correlate with the degree of pain, stiffness, or swelling present in the joints.

Rheumatoid arthritis is a common rheumatic disease, affecting approximately 1.3 million people in the United States, according to current census data. The disease is three times more common in women as in men. It afflicts people of all races equally. The disease can begin at any age and even affects children (juvenile idiopathic arthritis), but it most often starts after 40 years of age and before 60 years of age. Though uncommon, in some families, multiple members can be affected, suggesting a genetic basis for the disorder.