Complex Regional Pain Syndrome is a debilitating condition that is characterised by continuous pain, that begins in one region of the body and usually has a distal predominance of sensory, motor, autonomic, skin and bone abnormalities in the affected region.  The pain is disproportionate, in time or degree, to the inciting event.1,2   There is variable progression in the signs and symptoms over time. 

CRPS is usually precipitated by a trauma, such as an accident, fracture, a surgery, or following a medical emergency such as a heart attack or a stroke, but CRPS can also occur after a very trivial incident or immobilisation and, on occasion, can develop spontaneously.

CRPS Type I develops after any type of trauma, especially fractures and soft tissue lesions, such as crush injuries, and has no identifiable nerve damage.

CRPS Type II occurs after major nerve damage.

CRPS Type III (Not otherwise specified) includes patients who did not strictly meet the Budapest Clinical Criteria but whose signs and symptoms could not be better explained by any other diagnosis

The mechanism of CRPS is unknown,3 however, it is believed that CRPS occurs as a result of damage to, or a malfunction of the nervous system and the immune system at the site of the injury.

The earlier belief that CRPS was caused by a dysfunction of the sympathetic nervous system is no longer held as true, nor is the belief that CRPS occurs in defined stages4 Studies have shown no evidence of psychological risk factors for CRPS.3

CRPS is a multi-system disorder that affects the musculoskeletal system, the peripheral nervous system and the central nervous system.

Main Features

The onset of CRPS symptoms usually appear within one month of the inciting event.

The pain is often described as continuous and burning in nature and is made worse by movement, mechanical or thermal stimulation or by stress.  The level of pain is rated as one of the most severe on the McGill University Pain Index. The intensity of the pain may fluctuate, and allodynia (a painful response to non-painful stimuli) or hyperalgesia (increased sensitivity to pain) may be present.  Changes in skin colour or temperature may occur as well as unusual swelling and sweating.  There may also be trophic changes of the skin, hair, nails or bone growth.  Impairment of movement and joint mobility are frequently seen, and this can include weakness, tremors, spasms and in some cases dystonia (involuntary muscle contractions or repetitive movements).

Studies have shown that:3,5

  • 3 – 4 times more women than men are affected.

  • The arm is affected in about 60% of cases and the leg in about 40%

  • The overall estimated incidence of CRPS is 26.2 per 100,000 person-years (1 in every 3800)

  • CRPS affects all races; no difference in incidence or prevalence have been observed.

  • CRPS reaches its peak incidence in adults between 37 – 50 years of age

    • CRPS affects more adolescents, compared with children

    • The mean age of onset is 12.5 years of age

    • In paediatric patients the lower body is affected in 75% of cases

    • 30% of paediatric patients also have dystonia or movement disorders


  • Fractures account for approximately 45%

  • sprains 18%

  • elective surgery 12%.

  • Spontaneous onset is uncommon < 10%

*NB Spontaneous cases/unknown causes may be explained by minor injuries that have been forgotten.5


The disorder varies from mild and self-limiting to a chronic, progressive disease. CRPS can lead to sleep disturbances and emotional stress, both of which exacerbate the symptoms. It is often associated with substantial disability, loss of quality of life and great personal and societal economic burden.1,2

Over time, usually a period of years, many of the visible signs of CRPS, such as swelling, sweating, colour and temperature changes reduce although the pain and motor symptoms usually persist.  Despite the absence of some of these visible signs of CRPS, this is not a sign of remission.  If the pain persists the condition should still be considered active.

High resolution rates have been reported, but many studies contradict this6. Patients who still have ongoing pain and physical impairments 24 months after onset are considered to have the condition long-term.  A retrospective CRPS study showed that the majority of patients had persistent impairments at 2 years post onset.  At an average of 5.8 years post onset 16% reported the CRPS as still progressive and 31% were incapable of working.7

It has been shown that an early diagnosis, within 3 – 6 months, is key for the best possible outcome, however for many patients a CRPS diagnosis is delayed for months – years due to a lack of knowledge in the medical profession.

Relapses can occur after being symptom free for some time. Relapses can happen for no known reason or after a new trauma or surgery.

There is no cure for CRPS.

The McGill University Pain Index
1 Bharwani KD et al., Complex regional pain syndrome: diagnosis and treatment, BJA Education, 17 (8): 262–268 (2017)
2 Ganty P et al., Complex regional pain syndrome: recent updates, Continuing Education in Anaesthesia Critical Care & Pain, Volume 14, Issue 2, 1 April 2014, Pages 79–84, 
3 Marinus, J et al. “Clinical Features and Pathophysiology of Complex Regional Pain Syndrome – Current State of the Art. The Lancet. Neurology10.7 (2011): 637–648
4 Harden R. et al., Complex Regional Pain Syndrome: Practical diagnostic and Treatment guidelines, 4th edition, Pain Medicine 2013; 14:180 – 229
5 Gupta G. et al., Complex Regional Pain Syndromes Clinical Presentation: Background, Pathophysiology emedicine.medscape.com/article/1145318 update 21 June 2018
6 Bean DJ et al., The outcome of complex regional pain syndrome type 1: a systematic review. J Pain 2014;15(7):677–90
7 de Mos M et al., Outcome of the Complex Regional Pain Syndrome. Clin J Pain 2009;25(7):590–7