Hands and wrists are the most common location for deformities caused by rheumatoid arthritis. As joint damage progresses, the joints between the hand and fingers (metacarpophalangeal joints—MCPs) swell and move upward (dorsal subluxation). The tendons over the joints slip and cause the fingers to bend toward the little finger (ulnar drift). In addition, muscles in the hand thin and weaken, creating valleys between the long tendons.