Although complex regional pain syndrome (CRPS) has been a recognised medical condition for more than 150 years, its exact cause is still unclear.

Previous injury

The condition usually seems to develop within a month of an injury, either minor or more serious. These can include:

Most people recover from these injuries without experiencing any significant long-term effects, but people with CRPS develop pain that's much more severe and long-lasting than usual.

The pain can spread beyond the site of the original injury, usually affecting an entire limb. For example, CRPS may affect your whole arm after an injury to your finger or hand. In some cases, more than one area of the body can be affected.

CRPS has also been known to occur after surgery to a limb or after part of a limb has been immobilised (for example, in a plaster cast).

CRPS after an injury

It's not known why some people develop CRPS after an injury. Due to the complex nature of the symptoms, it's unlikely the condition has a single, simple cause.

Some people even believe CRPS shouldn't be regarded as a single medical condition, because the symptoms could be the result of several different ones.

One of the main theories suggests that CRPS is the result of a widespread abnormal response to an injury that causes several of the body's systems to malfunction, including:

  • the central nervous system  the brain and spinal cord
  • the peripheral nervous system  the nerves that lie outside the central nervous system
  • the immune system  the body's natural defence against illness and infection
  • the blood vessels  the series of arteries and veins that transport blood around the body

These systems are responsible for many body functions often affected in people with CRPS, such as:

  • detecting pain and transmitting pain signals
  • triggering inflammation (swelling)
  • controlling temperature and movement

It's also been suggested that some people may be more susceptible to CRPS because of genetic factors. However this isn't clear and it's very unlikely other members of your family will be affected if you have CRPS.

In the past, some people believed CRPS may be a psychological condition that makes people think they are experiencing pain. However, this theory has been largely disproven.

Page last reviewed: 16/05/2016

Next review due: 01/05/2019