Complex Regional Pain Syndrome, or CRPS, is a chronic condition of pain that usually affects arms, legs, hands or feet, often after an injury. Along with pain, there may be changes in skin color, temperature and swelling in the painful area. The cause of CRPS is believed to be connected to damage to or dysfunction of the central nervous system (brain and spinal cord) and peripheral nervous system (nerves in the rest of the body linked to the central nervous system).