Rheumatoid arthritis affects the cells that lubricate and line joints. This tissue – synovium- becomes inflamed and swollen. The swollen tissues stretch supporting structures of the joints such as ligaments and tendons. As the support structures stretch out, the joints become deformed and unstable. The joint cartilage and bone erode. Often the joints feel hot and look red. Rheumatoid arthritis of the hand is most common in the wrist and knuckles. The disease is symmetric, thus what occurs in one hand usually occurs in the other.