Rheumatoid arthritis (RA) is a common type of arthritis, found in over 1.3 million people in the United States. Often debilitating, it's a painful, chronic disease that damages the joints. The condition usually affects people ages 20 to 60, with women five times more likely than men to have it. RA typically is thought to occur when the immune system doesn't work as it should and attacks the membranes, which are the thin tissues that surround the joints. Researchers don't fully understand why this happens. The result is inflammation that's often marked by pain, swelling, and stiffness of more than one joint. Unlike osteoarthritis, RA frequently is "symmetrical" in that it affects both sides of the body at once. For example, you may feel pain in both hands and both hips.Symptoms may vary from person to person. There's currently no cure for RA. Some people go through cycles in which their RA flares up and is extremely painful, then quiets down, and then returns. Still others have continuous pain for many years. Additional symptoms such as fatigue and fever may accompany the disease.