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Oldies but Goodies – What is Complex Regional Pain Syndrome – in plain English



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Over this holiday season we are posting the most read articles from the last five years.  Here is the first.

What is Complex Regional Pain Syndrome – in plain English

What is Complex Regional Pain Syndrome? Well, complex regional pain syndrome (CRPS) is exactly that

Complex: Many, many different problems have been identified in people with CRPS. These problems can be severe and usually involve many of our biological systems.  This makes the situation complex.

Regional: The symptoms of CRPS are almost always confined to a particular region of the body. The arm of the leg is the most commonly involved region. Sometimes CRPS of one arm spreads to the leg on the same side of the body. Sometimes it spreads to the opposite arm, in which it usually ‘mirrors’ the other one.

Pain: CRPS is exquisitely, severely, painful. Like the other symptoms, the pain is confined to the affected limb or limbs.  Often the skin is too tender to touch and the whole limb is too painful to move. In fact, sometimes the limb is too painful to even imagine moving [1,2].

Syndrome: A syndrome is a pattern of symptoms that often occur together.  Normally, the reason that something is called a syndrome is that we do not know what causes it, we just know that this pattern of symptoms occurs together and usually at the same time.

So, CRPS is the name given to a pattern of symptoms that often occur together.

Diagnosis of CRPS

Because CRPS is not based on a particular injury, bacteria, virus, or other identifiable cause, diagnosis of CRPS relies on the symptoms and signs (what’s the difference between signs and symptoms? – see Note 1 at the end of the article) Not all the signs and symptoms are always present. So, the official position established and endorsed by the International Association for the Study of Pain is that we should use this checklist:

Symptoms and Signs of CRPS
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To be diagnosed with CRPS, the following criteria have to be met:

  1. The compulsory item is ticked
  2. At least one symptom in each group of symptoms is ticked.
  3. At least one sign in 2 or more of the groups of signs is ticked.

So, this means that you can not really diagnose yourself with CRPS based simply on your symptoms.  There is no added diagnostic value of: x-rays, bone scans, blood tests, sympathic function tests, quantitative sensory testing, nerve conduction tests.

How many people have CRPS?

No one really knows how many people have CRPS, but some really good research studies give us a rough idea.  For example, one really good study, undertaken in The Netherlands [3] suggests that, every year, one person in every 4000 will develop CRPS.  That doesn’t really sound like many, but it means that about 5000 Australians, 20 000 Brits and 75 000 Americans, will get diagnosed with CRPS this year.  That is how many people will get it.  How many people will actually have it in any given year? In crude terms, you can just multiply that number by 5 – 25 000 Australians, 100 000 Brits and 400 000 Americans.  Now the numbers look big. They look even bigger when you consider that treatment for each patient with chronic CRPS costs about AU$12,000 per year and total lost income due to CRPS in Australia (a small country by population standards) exceeds $1 billion [4].   So, if you are someone with CRPS, you are not, by any means, alone. If you are someone trying to decide whether to fund CRPS research, you surely should!

What causes CRPS?

We don’t know this either.  One theory suggests that something goes wrong with the inflammatory response after a minor injury so that it just winds up and up until the whole protective system is very very sensitive.  Another theory is that CRPS results from psychological weakness and another that it relates to certain personality types.  The last two theories have been proven wrong – in the largest study, these things were not related to having CRPS: pre-injury psychological profile (including ‘personality’), biomechanical factors (the specific size, shape, configuration and movement of your body parts), injury characteristics (how and what you injured), surgical approaches (what operation, if any, they did), compensation and previous illness history [3].  The first theory has neither been proven wrong, nor proven right. Both seem possible.  It is also possible that there are several potential causes of CRPS. We really don’t know.

What we do know is that the response to tissue trauma (injury) is excessive.  We know that the autonomic nervous system (the system that controls blood flow to your body) is involved, most probably by altered sensitivity to adrenaline.   We know that the immune system is involved. We know that the system that controls movement is involved.  Last, but not least, we know that the pain system is involved.

Acute CRPS seems different to chronic CRPS

In acute CRPS, temperature changes almost always involve the limb being hotter than normal and hotter than the other one, and being redder than normal.  As CRPS progresses, a cold and white limb becomes more common and people often notice that the hair or nails, or both, on that limb, are growing faster than normal and faster than the other limb.  Chronic CRPS is also associated with other evidence of dysfunction within the central nervous system, including the brain.  For example, there is some evidence that people with chronic CRPS think that their affected limb is bigger than it really is; they often feel as though the limb doesn’t belong to them anymore; the sensory system can develop errors so that one can’t be sure exactly where on the limb one has been touched unless they are looking at it; it can become more and more difficult to move, develop the shakes, or become ‘stuck’.  These are all things that are distressing but they are also things that we think can be treated with appropriate rehabilitative treatments – although the evidence is weak because it is a very recent direction in treatment.

What is the best treatment for CRPS?

In order to determine if a treatment is effective, it must be tested with the strongest experiments possible.  Although many treatments have been used for CRPS, only a small few have been tested with strong experiments.  We can categorise treatments according to the results of experiments (See Table in Note 2):

Treatments for acute CRPS

  1. Anti-inflammatory therapies: Some are good, some a probably no good and some are definitely no good.
  2. Analgesics: Some might be good (eg ketamine intravenously or gabapentin) but there are no good experiments on it; some are no good (eg local anaesthetics, anti-epileptics, serotonin reuptake inhibitors).
  3. Spinal cord stimulators are probably good, although remember that there are risks with inserting a stimulator onto your spinal cord and many need revision or relocation.
  4. TENS is no good.
  5. Activation & mobilisation (eg physical therapies) are probably good as long as they promote movement and function, not targeting pain relief.
  6. Mirror therapy is probably good.

Treatments for chronic CRPS

  1. Spinal cord stimulators are probably good although remember that there are risks with inserting a stimulator onto your spinal cord and many need revision or relocation.
  2. Graded motor imagery is good (and also see graded motor imagery for pathologic pain)
  3. Tactile discrimination training might be good but there are no good experiments on it (see also our other paper on tactile discrimination).
  4. The other things that are listed for acute CRPS are not effective for chronic CRPS.

Where can I tell my doctor or physiotherapist to look for more information on treatment guidelines?

There are official guidelines developed in The Netherlands. The guidelines are a little out of date but the best around (http://pdver.atcomputing.nl).  The RSDSA association has a bundle of resources for clinicians and patients. BodyInMind has resources for clinicians, including teaching materials and publications.

What research is being done?

The most impressive concerted research effort involving CRPS is going on in the Netherlands. It is called TREND and you can have a look here. Also, the National Institute of Neurological Disorders and Stroke (NINDS) and other institutes of the National Institutes of Health (NIH) conduct research relating to CRPS in laboratories at the NIH and also support additional research through grants to major medical institutions across the country. NINDS-supported scientists are studying new approaches to treat CRPS and intervene more aggressively after traumatic injury to lower the chances of developing the disorder.  The Australian National Health & Medical Research Council funds clinical studies into CRPS after wrist fracture.


1. Signs and Symptoms

Signs are things that someone else can observe. Symptoms are things that you feel. For example, feeling cold is a symptom.  Actually being cold is a sign.

2. Evidence that something works

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Evidence that something doesn’t work

Brief Pain Inventory (BPI) long
Brief Pain Inventory (BPI) short
Depression Anxiety and Stress Scales (DASS)
Pain Self-Efficacy Questionnaire (PSEQ)
Pain Catastrophizing Scale (PCS)
Numerical Rating Scale (NRS)
Visual Analogue Scale (VAS)
Faces Pain Scale (FPS)
West Haven-Yale Multidimensional Pain Inventory (WHYMPI)
Pain Disability Index (PDI)
Roland Morris Disability Questionnaire (RMDQ) Translations
Oswestry Disability Index (ODI)
Neck Disability Index (NDI)
Beck Depression Inventory (BDI)
Hospital Anxiety and Depression Scale (HADS)
Patient Global Impression of Change (PGIC)
Neck Disability Index (NDI)


  1. Moseley, G.L. (2004). Imagined movements cause pain and swelling in a patient with complex regional pain syndrome. Neurology 62, 1644.
  2. Moseley, G.L., Zalucki, N., Birklein, F., Marinus, J., Hilten, J.J.v., and Luomajoki, H. (2008). Thinking about movement hurts: The effect of motor imagery on pain and swelling in people with chronic arm pain. Arthritis Care & Research 59, 623-631.
  3. de Mos, M., de Bruijn, A.G.J., Huygen, F.J.P.M., Dieleman, J.P., Stricker, B.H.C., and Sturkenboom, M.C.J.M. (2007). The incidence of complex regional pain syndrome: A population-based study. Pain 129, 12-20.
  4. Kemler, M.A., and Furnee, C.A. (2002). The Impact of Chronic Pain on Life in the Household. Journal of Pain and Symptom Management 23, 433-441.

Lorimer Moseley (2009). What is Complex Regional Pain Syndrome – in plain English BodyInMind

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