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Harvard Medical School

complex regional pain syndrome (crps)

What Is It?

Complex Regional Pain Syndrome (CRPS) is a painful and long-lasting condition. CRPS usually causes severe, constant, burning pain in the affected arm or leg.

The cause of CRPS remains unknown. However, this condition can be triggered by damage to nerve fibers in tissue that has been injured.

Experts believe that in CRPS, nerves become overly sensitive. Painful signals become more painful. And common stimuli, such as light touch and temperature changes, also are experienced as pain.

This condition usually starts after an injury or other event. Examples include trauma, fracture, infection, surgery, stroke or wearing a plaster cast.

Often, the injury that triggers CRPS is mild compared with the pain that follows it. However, the condition also can follow more severe injury or paralysis. The pain often is not limited to the area that was injured.

This condition can occur at any age. It is relatively rare.

CRPS has been called by many other names. These include reflex sympathetic dystrophy syndrome (RSDS), algodystrophy, causalgia, shoulder-hand syndrome, Sudeck's atrophy and transient osteoporosis. There are two types of CRPS:

• Type I – there is no nerve damage present

• Type II – a nerve abnormality can be detected

Although the name was officially changed from RSDS to CRPS, the name change has not been universally accepted.