Complex regional pain syndrome, formerly known as reflex sympathetic dystrophy or causalgia, is a difficult therapeutic problem for the orthopaedic surgeon treating an affected lower extremity. Despite many divergent and often conflicting theories, the cause of the severe pain, alterations in regional blood flow, and edema is unknown. Interventions that have proved successful for treating similar conditions in the arm and hand frequently do not relieve pain similarly in the lower extremity. Common treatment regimens target individual components of this symptom complex, namely, sympathetic or afferent nerve hyperactivity, vasomotor instability, or regional osteoporosis. Despite widespread use of some of these treatments, few controlled clinical trials quantify their effectiveness. This challenging syndrome is best managed by a multidisciplinary team, including chronic pain management specialists, physical therapists, and orthopaedic surgeons.