Burning Nights CRPS Support is a UK national charity dedicated to raising awareness of Complex Regional Pain Syndrome (CRPS)

Complex Regional Pain Syndrome (CRPS) or Reflex Sympathetic Dystrophy (RSD)

What Is CRPS or RSD?

Complex Regional Pain Syndrome or CRPS was formerly known as Reflex Sympathetic Dystrophy or RSD. It is considered to be a multi-system syndrome or condition that is mainly characterised by chronic pain that lasts for a long time after the normal length of time for healing.

CRPS usually begins in one area of the body, but it can affect any part of the body. CRPS will usually begin in one particular area of the body, but can then spread away from the initially damaged area, even if it remains in one limb.

In the United Kingdom, the main guidelines that are used and followed are the Royal College of Physicians (RCP) Guidelines for complex regional pain syndrome in adults. These RCP Guidelines for CRPS were updated in July 2018.

According to the Royal College of Physicians (RCP) Guidelines for CRPS (2018), they state that Complex Regional Pain Syndrome (CRPS) is:

Complex regional pain syndrome (CRPS) is a debilitating, painful condition in a limb, associated with sensory, motor, autonomic, skin and bone abnormalities.

From the Royal College of Physicians’ (UK) guidelines for CRPS (2018)it can be said that CRPS is:

  • A debilitating painful chronic condition in a limb or extremity
  • It is associated with sensory, motor, autonomic, skin & bone abnormalities
  • Pain is the leading symptom and is usually out of proportion to the original or inciting event
  • It is often associated with limb dysfunction
  • It causes psychological distressCRPS is not caused by psychological issues or mental health problems. CRPS used to be thought of as a condition that developed from a psychological disorder. However subsequent research has shown that this is untrue. CRPS is not a psychological disorder. However complex regional pain syndrome does subsequently cause mental health issues.
  • It often arises after an injury to a limb

Complex Regional Pain Syndrome, formerly known as Reflex Sympathetic Dystrophy, was first described in the mid-16th Century. However it was then later more commonly known in the descriptions during the American Civil War by Silas Weir Mitchell.

For more information about the history of CRPS, why not visit What is CRPS/RSD


Is CRPS and RSD The Same Condition?

Yes they are the same condition.

Over the last five centuries that CRPS has been described, it has had over 200 different names in the English language alone.

CRPS is the current name for this condition. However the previous name before CRPS was RSD or Reflex Sympathetic Dystrophy.

RSD is now what is known as CRPS Type 1 or CRPS 1.

What Types of Complex Regional Pain Syndrome (CRPS) Are There?

There are two (2) main types of CRPS. However there is a third sub-type of Complex Regional Pain Syndrome (CRPS) (Merskey, H, et al 1994). These are:

Type 1 or CRPS I

CRPS I or Type I used to be known as Reflex Sympathetic Dystrophy (RSD). There are still many people including doctors and specialists who still refer to CRPS as RSD.

CRPS I or CRPS Type I, occurs after an illness or an injury that did NOT directly damage a nerve. It usually occurs after a minor or major tissue injury to the extremities.

Type 1 will usually develop from injuries including (but not limited to) soft tissue damage, sprains or fractures (not nerve related).

According to the Mayo Clinic’s web page Complex Regional Pain Syndrome, they say:

 “About 90 percent of people with complex regional pain syndrome have type 1.”  


Type 2 or CRPS II

CRPS Type II or CRPS II used to be known as CAUSALGIA. CRPS Type II occurs after there has been an actual known injury to a nerve.

Even though there are the 2 types of CRPS, formerly RSD, the signs and symptoms are almost the same for both types. Have a look at the Signs and Symptoms page to learn more about the signs and symptoms of Complex Regional Pain Syndrome (CRPS).


According to the Budapest Criteria, there is another diagnostic type of crps or rather sub-type of CRPS which is CRPS – Not Otherwise Specified or CRPS-NOS.

This 3rd sub-type of CRPS, CRPS-NOS, was added because approximately 15% of patients previously diagnosed with CRPS (based on 1994 IASP criteria) would not fully meet the new clinical diagnostic Budapest Criteria (Sebastin, S.J. et al 2011)

According to the RCP UK guidelines (2018) CRPS-NOS is a type of CRPS:

“…for patients who do not fully meet the criteria but whose signs and symptoms could not be explained better by another diagnosis. For patients who fulfilled the Budapest criteria in the past but no longer do so, the term CRPS-NOS may also be used. “


Hot/Warm, Intermediate or Cold/Blue Complex Regional Pain Syndrome (CRPS)

You may also hear other expressions concerning Complex Regional Pain Syndrome (CRPS) which are: Warm / Hot CRPS, Intermediate CRPS and Cold/Blue CRPS. These 3 terms are seen as diagnostic terms or sub-groups of CRPS rather than symptoms of the condition.

Warm/Hot/Red CRPS

The warm or hot type of CRPS is seen by Doctors and specialists as the ‘acute’ phase of the affected CRPS limb or CRPS area.

The majority of CRPS sufferers are often classed in this hot or warm type. 70% of CRPS sufferers will have the warm or hot type CRPS and 30% will have the Cold CRPS (Eberle, T et al 2009).

According to a recent study by Dirckx, M et al (2015) the warmer CRPS side:

” …inflammation is generally assumed to be present “

If diagnosis is made early or if symptoms have appeared soon after injuries, surgery or otherwise then the term of hot or cold is sometimes used by doctors and specialists.

There will usually be a distinct temperature difference between the CRPS affected limb and the non affected limb or limbs. Most crps sufferers won’t have been told of their hot or cold type this may have been because diagnosis was too late.

At the initial stages of complex regional pain syndrome, sufferers with CRPS Type I will often have a warmer affected limb. However eventually when the Type I becomes chronic, the CRPS affected limb will then turn cold.

In the warm/hot phase of CRPS it will often display the classic signs of inflammation (Veldmen, P.H. et al 1993.) You will also find a greater pressure hyperalgesia on the affected CRPS limb or area. (Vaneker, M. et al 2005)

According to Wasner, G et al. (2001) :

“…in CRPS I, unilateral inhibition of sympathetic vasoconstrictor neurones leads to a warmer affected limb in the acute stage.” 


Intermediate CRPS

Imtermediate Complex Regional Pain Syndrome (CRPS) is where the CRPS affected limb or area is neither warm/hot nor cold/blue. (Wasner, G. et al 2001) (Dirckx, M et al 2015)

Cold or Blue CRPS

The term Cold CRPS or Blue CRPS is usually is referred to in the chronic stages of complex regional pain syndrome.

Bruehl, S. et al (2010) found that the transition from warm/red CRPS to cold/blue is common in CRPS. CRPS patientswith this type will have lower McGill Pain Questionnaire (MPQ) results showing that there is increased central nervous system involvement as well as a higher chance of dystonia.

If you have been diagnosed with CRPS Type II (also known as Causalgia) you will most likely have had a diagnosis much earlier than patients with CRPS Type I.

This is because for those living with CRPS Type II, there has been a known direct injury to a nerve, therefore it will increase the probability of vasoconstriction causing the cold temperature straight away.

Unfortunately if you have been diagnosed with Type I Cold CRPS a study by Vaneker, M. et al (2005) stated that:

“…cold CRPS 1 patients have poorer clinical pain outcomes and show persistent signs of central sensitisation correlating with disease progression. The latter is not the case for warm CRPS 1 patients.” 

Again in the research study by Wasner, G. et al (2001) they said this about the cold CRPS Type I:

“Secondary changes in neurovascular transmission may lead to vasoconstriction and cold skin in chronic CRPS I, whereas sympathetic activity is still depressed.” 

How Does CRPS Develop?

Here’s a diagram to help explain how Complex Regional Pain Syndrome develops and the cycle the CRPS goes in. The diagram shows that:

  • The original injury initiates a pain impulse carried by the sensory nerves to the central nervous system
  • The pain impulse in turn triggers an impulse in the sympathetic nervous system, which returns to the original site of the injury
  • The sympathetic impulse triggers the inflammatory response causing the vessels to spasm and leads to swelling and increased pain
  • The pain triggers another response establishing a cycle of pain and swelling
  • Resulting condition with redness, swelling and lower temperature (Please visit Signs and Symptoms page for more details on symptoms)
What is CRPS | What is RSD? | CRPS cycle | Burning Nights CRPS Support
What is CRPS? | What is RSD? | CRPS cycle | Burning Nights CRPS Support | RSD CRPS

As you can see there are two main types of CRPS, which are Type I and Type II. There is a 3rd sub-type which is CRPS-NOS or CRPS Not Otherwise Specified.

The terms hot or warm CRPS, intermediate CRPS and cold CRPS are not seen as complex regional pain syndrome sub-types, but more of an explanation of the stages that a person living with Complex Regional Pain Syndrome goes through in each type ie from acute phase to chronic phase.


Other CRPS Information To Read

After being diagnosed with complex regional pain syndrome it can seem extremely daunting and frightening, leaving you feeling vulnerable.

However we have produced a lot of evidence based information to help you learn about your condition, how the condition can be managed as well as CRPS blogs helping you learn to live with your chronic condition.

Here is just a few CRPS articles for you to read:

Cited Resources


Last Updated: 23/07/2020

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