Rheumatoid arthritis, also known as RA or inflammatory arthritis, is a disease that attacks the joints, their surrounding tissues, and organs within the body. It causes the same pain from joint destruction that osteoarthritis produces, but by a different mechanism. Researchers believe RA is triggered by an autoimmune reaction, when certain cells within the body are mistakenly believed to be foreign and are directly attacked by the immune system. RA is a chronic condition; it slowly invades the joints throughout the body. However, symptoms may come and go, coming in waves of swelling and pain. Typical deformities can often be seen in other parts of the body, especially the hands.