Complex regional pain syndrome (CRPS) is a chronic condition marked by continuous, intense pain that tends to worsen over time. It usually occurs after a significant trauma to an arm or a leg, such as a fracture, but may also develop after no apparent injury. It is characterized by burning or aching pain along with inflammation, skin discoloration, altered temperature, abnormal sweating and hypersensitivity of the affected area that persist longer than the anticipated healing time for that injury.

There are two types of CRPS. They were formerly known as reflex sympathetic dystrophy syndrome and causalgia.

The cause of CRPS is not known. Some scientists believe it may result from damage to the nervous system, whereas others suggest it is triggered by an immune system response.

There is no known cure, but treatments such as medications, physical therapy, electrical stimulation, biofeedback and injection therapy are available. Patients who have symptoms of CRPS should seek medical attention promptly, as treatment is most effective when started soon after symptoms first appear. Left untreated, CRPS can become disabling.