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Complex regional pain syndrome (CRPS) is a rare condition that causes a long-term burning pain in a limb or part of a limb. CRPS used to be known as reflex sympathetic dystrophy. The areas that are usually affected are the arms. legs, hands and feet.

CRPS causes a severe, continuous pain that can make the affected part of the body difficult to use. The skin of the affected area can also become very sensitive, so that even the slightest touch or change in temperature can cause intense pain. See CRPS - symptoms for more information.

Types of CRPS

There are two types of CRPS that have different causes. They are:

  • Type one CRPS is triggered by a simple injury, such as a sprained or fractured ankle, where there has not been any nerve damage.
  • Type two CRPS is triggered by a more serious injury or procedure, where nerve damage has occurred following, for example, a broken bone, a serious infection or an operation

The injury causes pain that is much worse than expected. About 90% of all cases of CRPS are type one CRPS.

How common is CRPS?

It is difficult to estimate the exact number of people who are affected by CRPS because the condition can be difficult to diagnose. See CRPS - diagnosis for more information.

Estimates of CRPS from across the world vary, from one 1 in 18,000 people being affected to 1 in 4,000 people. Neuropathic pain, which is pain caused by problems with the body's nerves, is thought to affect one or two people out of every 100 in the UK.

CRPS is more common in women and people who are 50 to 70 years of age. However, the condition can affect people of any age, including children.


Your treatment for CRPS will usually be co-ordinated by a number of different healthcare professionals working together, such as a pain relief specialist and a physiotherapist. Treatment will involve a combination of:

  • physiotherapy - physical techniques, such as massage and manipulation, to help improve the movement in the affected body part
  • medicines to help relieve your pain

Treatment for CRPS is usually most effective when started immediately after diagnosis. See CRPS - treatment for more information about the different treatment options available.

Chronic usually means a condition that continues for a long time or keeps coming back.

Nervous system
The brain, spinal cord and nerves.

Neuropathic pain
Neuropathic pain is caused by problems with the body's nerves, either because the nervous system is not working properly or because the nerves themselves have been damaged.

Remission is when the symptoms of a condition are reduced (partial remission) or go away completely (complete remission).

Symptoms of complex regional pain syndrome

The main symptom of chronic regional pain syndrome (CRPS) is a severe, continuous burning pain in part or all of a limb. This could be in one of your arms, legs, hands, feet or ankles.

The pain is usually triggered by an injury, and is a lot worse than you would normally expect. For example, you may have a minor ankle sprain, but the pain can feel like a severe burn.

If you have CRPS, the skin of the affected body part can become very sensitive, and even the slightest touch, bump, or change in temperature can provoke a feeling of intense pain.

You may hear this described in the following medical terms:

  • hyperalgesia - when you are extremely sensitive to pain
  • allodynia - when you feel pain from something that should not be painful at all, such as a very light touch

In more severe cases of CRPS, the muscles in the affected limb may begin to wither (atrophy). This usually occurs if the person affected is unwilling to use their limb due to the associated pain.

Other symptoms

CRPS can cause some other symptoms, including:

  • alternating changes in skin temperature - sometimes your skin may feel sweaty, while at other times it may feel cold and clammy
  • changes in skin colour - your skin tone may range from pale and colourless to pink, or it may have a blue tinge and appear blotchy or streaky
  • changes in skin texture - your skin may appear shiny and thin
  • changes in the way that your hair and nails grow - they may grow unusually slowly or unusually quickly
  • swelling, pain and stiffness in the affected joints
  • increasing difficulty moving the affected body part

Stages of CRPS

The symptoms of CRPS usually progress in three distinct stages. However, not everyone will experience all of the possible symptoms, or progress through all three stages. The three stages of CRPS are outlined below.

Stage one

The first stage usually lasts from one to three months, and is characterised by an intense, burning pain in one of your limbs. You may experience:

  • muscle spasms (when your muscles contract tightly and painfully)
  • joint stiffness
  • rapid growth of hair and nails

The blood vessels in your limb will also be affected, causing a change in skin colour and temperature.

Stage two

The second stage of CRPS usually lasts from three to six months. The pain in your affected limb may get worse, and the skin colour and texture changes may be more pronounced. Symptoms of swelling and stiffness become more severe, and the muscle tone in your affected limb will begin to weaken.

Stage three

The third stage of CRPS is the last stage of the condition. At this point, any changes to your affected limb are likely to be irreversible. These may include:

  • significant loss of muscle tone in the affected limb
  • the bones of the limb may have become contorted (bent out of shape)
  • the joints in the affected limb may be stiff
  • you will probably find it very difficult to use or move your limb

Fortunately, with prompt and effective treatment, it is possible to stop the progression of CRPS to its final stage, preventing irreversible damage from occurring.

Joints are the connection point between two bones that allow movement.

Blood vessels
Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.

Causes of complex regional pain syndrome

Even though complex regional pain syndrome (CRPS) has been a recognised medical condition for more than 150 years, its exact cause is still unclear. The condition is usually triggered by an injury or trauma (damage to the body's tissues). For example:

  • A tissue injury with no nerve damage, such as a sprained ankle, can lead to type one CRPS (triggered by a minor injury).
  • A peripheral nerve injury (when a nerve in one of your limbs is damaged), such as a broken bone, can lead to type two CRPS (triggered by a more serious injury).

Why CRPS develops as a result of these injuries is still unknown. However, due to the complex nature of the symptoms of CRPS, most experts believe that it is unlikely that the condition has a single cause, and that it is more likely that the condition is caused by a combination of related factors.

Some experts believe that it may be a mistake to regard CRPS as a single medical condition, as there could be a number of different conditions that all cause the same symptoms. Some of the theories that have been suggested as possible causes of CRPS are described below.

Psychological abnormalities

A number of psychologists, including Sigmund Freud, have suggested that CRPS may be a psychological condition. CRPS could be the result of an unidentified underlying psychological trauma or difficulty that makes people think that they are experiencing pain.

However, this theory has been largely discredited because research shows that people with CRPS undergo physical changes in their nervous system, making it very unlikely that the condition is "all in the mind".

Furthermore, as most people with CRPS do not have a history of serious mental illness, it would be uncharacteristic for them to suddenly develop a psychological condition.

Sympathetic nervous system malfunction

Another theory is that CRPS is caused by a malfunction of the sympathetic nervous system.

The sympathetic nervous system is the part of the nervous system that is responsible for triggering your "fight or flight" reflex. This is a series of physical changes that your body undergoes when faced with a stressful or dangerous situation.

For example, if you were suddenly confronted by a vicious dog, your sympathetic nervous system would increase your:

  • heart rate
  • breathing rate
  • blood pressure
  • levels of certain hormones, such as adrenalin (a stress hormone)

This gives you a short-term release of energy, which can be helpful in either confronting or avoiding potential danger.

This theory suggests that an initial physical injury may cause your sympathetic nervous system to release chemicals known as catecholamines. Catecholamines are hormones, like adrenalin, that your body releases during stressful situations, as part of the "fight or flight reflex" explained above.

Due to some unknown underlying problem, the catecholamines are thought to activate pain receptors, which are special nerve endings that transmit pain signals to your brain.

This may explain why people with CRPS often experience post-injury pain that is out of all proportion to the initial injury. It is not the injury itself that is causing the problem, but your body's abnormal response to it.

As the sympathetic nervous system also helps to regulate the blood vessels in your skin, a malfunction of this system may also account for the other associated symptoms of CRPS, such as the changes in skin colour and temperature.

However, there have been some cases of CRPS, particularly type two, where there was no evidence of a problem with the sympathetic nervous system. Therefore, it may not be a factor in all cases.

Immune system malfunction

Another theory states that type two CRPS may be the result of the immune system not working properly. When an injury occurs, the immune system causes the affected area of your body to swell in order to help prevent the spread of infection. This process is known as inflammation.

The theory states that for reasons unknown, inflammation persists long after the injury has healed. This irritates the nerves in the affected area of your body, leading to severe, burning pain. Inflammation would also explain the changes that occur in the blood vessels.

Other possible causes

Other theories that may help to explain the cause or development of CRPS include:

  • genetic factors - some people may be more susceptible to CRPS because of genetic factors
  • limb disuse - if you are not using the affected limb enough, CRPS may be more likely to occur following an injury
  • treatment related - the treatment for the initial injury or trauma may have contributed to the CRPS - for example, a plaster cast that was too tight
  • oxidative stress - tissue damage that is caused by free radicals (a toxic waste product that is a natural by-product of cell activity), which are produced in large quantities by the inflammation after the injury

Blood vessels
Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.

Free radicals
Oxygen free radicals are a toxic waste product that is produced as a natural by-product of cell activity.

Genetic is a term that refers to genes. Genes are the characteristics inherited from a family member.

Hormones are groups of powerful chemicals that are produced by the body and have a wide range of effects.

Immune system
The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Nervous system
The brain, spinal cord and nerves.

Periphery nerves
The periphery nerves are a network of nerves that run from the brain and spinal cord and carry impulses to and from the rest of the body, such as the limbs and organs. They are responsible for the body's senses and movements.

Diagnosing complex regional pain syndrome

There is no single diagnostic test for complex regional pain syndrome (CRPS). The condition is usually diagnosed through a process known as "diagnosis of exclusion". This means that a confident diagnosis can only be made after other conditions that can cause similar symptoms have been ruled out through testing.


Possible tests used to rule out other conditions are:

  • blood tests, which can rule out an underlying infection or rheumatoid arthritis (a condition that causes pain and inflammation in the joints)
  • a magnetic resonance imaging (MRI) scan, where a strong magnetic field and radio waves are used to produce detailed images of the inside of your body, which can help to rule out underlying problems with your tissue or bones
  • a biopsy, where a small tissue sample is removed and checked for the presence of abnormal cells
  • an X-ray, an imaging technique that uses high-energy radiation to highlight bone and tissue abnormalities, and can help to rule out problems with the joints and bones

There are other tests that, while they cannot prove that you have CRPS, may indicate that there is a good chance that you have developed it. These are described below.

  • A physical examination, where your GP or another specialist will check for physical signs of CRPD, such as swollen joints, and changes to your skin's temperature and appearance.
  • Sweat testing, where the sweat that is produced by both your affected limb and an unaffected limb is measured. A large difference between the two readings could indicate CRPS.
  • Thermography, where an infrared thermometer is used to measure your skin temperature at different parts of your body. If your affected limb has a much higher, or lower, skin temperature than the rest of your body, it could indicate CRPS.
  • Electrodiagnostic testing, which involves a series of tests where wires are attached to your skin in order to measure the electrical activity of your nerves. Abnormal readings may suggest that your nerves are damaged, and that you have type two CRPS.

Diagnostic checklist

As CRPS can be a difficult condition to diagnose, experts in the field have created a checklist to assist GPs and other healthcare professionals when making a diagnosis.

A diagnosis of CRPS can be made if all of the following signs and symptoms are present:

  • You have recently experienced an injury or other type of trauma.
  • You have ongoing pain in a limb that is disproportionate to the original injury or trauma.
  • There is physical evidence of swelling, and changes to your skin temperature and appearance.
  • No other diagnosis would better explain your signs and symptoms.


If you are diagnosed with CRPS, you may be urgently referred to a specialist pain clinic. There are around 300 pain clinics in the UK, which are mostly located in hospitals. An urgent referral ensures that treatment can be started immediately, because the earlier your treatment is started, the less likely it is that you will experience any long-term disability.

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Joints are the connection point between two bones that allow movement.

Damage to the body's tissues.

Treating complex regional pain syndrome

The treatment of complex regional pain syndrome (CRPS) usually involves a combination of physical treatment methods and medication to manage the pain.

Your treatment will usually be co-ordinated by a multi-disciplinary team (a number of different healthcare professionals working together). See the box to the right for more details about who may be involved in your treatment.


Many experts feel that physiotherapy is the most important factor in treating CRPS. The aim of physiotherapy is to:

  • improve, or restore, movement to the affected body part
  • prevent muscle wastage
  • prevent contortion of the bones (when the bones are bent out of shape)

Your physiotherapist (a healthcare professional who is trained in the use of physical methods, such as massage and manipulation, to promote healing) will teach you a range of exercises. These will gradually improve the strength and flexibility of the affected body part.

Initially, physiotherapy can be very painful, but research has shown that the symptoms of pain tend to improve significantly for people who persist with physiotherapy.

See the Health A-Z topic about Physiotherapy for more information about this type of treatment.

Graded motor imagery

A review of a number of different techniques used in physiotherapy found that graded motor imagery may be most effective for reducing pain in people with CRPS.

Graded motor imagery aims to change the way your brain thinks about pain. There are three steps to this treatment, which are described below.

  • Step one: testing your "laterality" (your ability to tell left from right). This is where you teach your brain to recognise right and left images, for example by correctly identifying a picture of a left hand or a right hand.
  • Step two: "motor imagery" (imagining movements, or watching other people move). As you watch other people move you imagine that it is you doing the movement.
  • Step three: mirror therapy (a mirror is used to reflect the 'good' limb). For example, if your left hand is causing you pain, it is placed in a mirror box so that your right hand (the "good" hand) is reflected. Your brain sees two "good" images and is tricked into thinking that your left hand no longer hurts.

Mirror therapy is sometimes used when people have had a limb amputated to help with phantom limb pain (a sensation that their limb is still attached to their body and is causing them pain). Mirror therapy has also been found to be effective in CRPS, and works best after following the first two steps which help prepare the brain for this type of treatment.

While mirror therapy has been used in physiotherapy for some time, graded motor imagery is a relatively new technique and it may not be available from your local primary care trust. If it is available, your physiotherapist will discuss the technique with you if they think that it may be beneficial.

Occupational therapy

An occupational therapist can help to identify problem areas in your everyday life, such as dressing yourself or getting to the shops. They can then help you to work out practical solutions that will enable you remain independent.

For example, if you are experiencing pain in one arm, an occupational therapist will be able to teach you how to complete activities one-handed. Alternatively, they can find ways for you to continue using your arm by practising certain movements.

Pain relief

There are a number of medicines that have proved successful in treating the pain of CRPS. Your GP or pain specialist will discuss these with you, as well as the possible side effects of each, in order to find a programme of medicine that is effective.

In treating CRPS, a step-wise approach to pain management is usually recommended. This means that your treatment team will try lower strength painkillers first, and will only use stronger painkillers if they are necessary.

Alternatively, a short-term course of strong painkillers may be used so that you are able to begin physiotherapy. Once you begin to respond to the positive effects of physiotherapy, you move on to weaker painkillers. Some pain relief treatments are discussed below.

Non-steroidal anti-inflammatory drugs (NSAIDs)

The first type of painkillers that are often used to treat the pain of CRPS are over-the-counter (OTC) painkillers called non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen.

People are often surprised that NSAIDs are recommended to treat severe pain. However, they have been shown to be very effective in relieving the symptoms of CRPS in many people. They can also help to reduce any associated swelling.

See the Health A-Z topic about NSAIDs for more information about this type of medicine.

Nerve blocks

Nerve blocks are often used to provide short-term pain relief for people with CRPS. A nerve block involves injecting local anaesthetic into a group of affected nerves. This prevents the pain signals from reaching the brain. A reduction in pain often continues even after the effect of the local anaesthetic has worn off.

Side effects of a nerve block can include:

  • a rash
  • itching
  • weight gain
  • soreness at the site of the injection
  • bleeding

Although nerve blocks are considered a standard treatment for CRPS, there is a lack of research into how effective they are.

For example, one older study found that nearly half of people with CRPS might not get any pain relief from this form of treatment. Moreover, a more recent review could not find enough research into nerve blocks for CRPS to make any definite conclusions about their effectiveness.


Anticonvulsants were originally designed to treat epilepsy (a condition that causes seizures or fits). However, they have also been found to be useful for treating nerve pain. Gabapentin is the most widely used anticonvulsant for treating CRPS.

Possible side-effects of gabapentin include:

  • drowsiness
  • dizziness
  • tiredness
  • loss of co-ordination

Do not drive, or operate heavy machinery, if you find that gabapentin is making you drowsy.

You should not suddenly stop taking gabapentin because you will experience withdrawal symptoms. These could include:

  • anxiety
  • insomnia
  • nausea
  • pain
  • sweating

If you want to stop taking gabapentin, or no longer need to take it, your GP will arrange for your dose to be slowly reduced over a week. Gradually reducing your dosage in this way will ensure that you do not experience withdrawal symptoms.

Tricyclic antidepressants (TCAs)

Tricyclic antidepressants (TCAs) were originally designed to treat depression, but like anticonvulsants, they were found to be effective in treating nerve pain. Amitriptyline is the most widely used TCA for treating CRPS.

You may have side effects when taking amitriptyline, including:

  • drowsiness
  • dry mouth
  • blurred vision
  • constipation
  • difficulty urinating

Do not drive, or operate heavy machinery, if you find that amitriptyline is making you drowsy. Amitriptyline should not be taken by people with a history of heart disease.

See the Health A-Z topic about Antidepressants for more information about this type of medicine.


If you are experiencing a severe episode of pain, opiates such as codeine and diamorphine can be used to provide short-term relief.

The long-term use of opiates is usually discouraged because of the potential side effects. However, there may be circumstances where the benefits of using opiates outweigh any associated risk.

The long-term use of an opiate does carry the risk that you will develop an addiction to the medication. Your dosage will therefore be carefully monitored to reduce this risk as much as possible, but it can never be entirely eliminated.

Other side effects of opiates include constipation and drowsiness - although this should improve as your body develops a tolerance to the opiate.

Do not drive or operate heavy machinery while taking opiates.

Spinal cord stimulation

Spinal cord stimulation is a possible treatment for neuropathic pain, which is pain that is caused by problems with the body's nerves. It involves having an operation to place a small device inside your body, usually under the skin of your tummy or buttocks.

The device produces mild electrical pulses that are sent to your spinal cord (a column of nervous tissue in the spinal column that sends messages between your brain and the rest of your body).

These pulses cause a stimulating effect that changes how you feel pain. You should feel a tingling sensation in the part of your body that usually hurts, which masks the pain. The level of stimulation can be adjusted as your pain improves or gets worse, and the device can be taken out if necessary.

A trial in people with type one CRPS found that, compared to physical therapy alone, spinal cord stimulation was more effective at reducing pain.

The National Institute for Health and Clinical Excellence (NICE) has issued guidance stating that spinal cord stimulation will only be considered if:

  • You are still experiencing pain after six months of trying other treatments.
  • You have had a successful trial of the stimulation.

Your multidisciplinary team will discuss spinal cord stimulation with you if they think that this treatment may benefit you.

Psychological treatments

Living with a chronic (long-term), painful condition can be very stressful and distressing, and people with CRPS may experience feelings of anxiety and depression.

It is important to look after your psychological wellbeing, because otherwise, as well as the adverse effect on your quality of life, feelings of depression and anxiety can interfere with your physiotherapy.

If you have been feeling very down during the past month, and you no longer take pleasure in the things that you used to enjoy, you may be experiencing depression. If this is the case, visit your GP.

Psychological therapies can also be useful in helping you to cope better with the symptoms of pain. For example, some studies have shown that a type of therapy called cognitive behavioural therapy (CBT) can help in the management of chronic pain.

CBT is based on the principle that the way a person feels is partly dependent on the way that they think about things. People who have trained themselves to react differently to their pain, by using relaxation techniques and maintaining a positive attitude, have reported that their pain levels decreased. They were also more likely to persist with their physiotherapy, which also helped to reduce their symptoms of pain.

See the Health A-Z topics about Depression and CBT for more information about these subjects.

The abdomen is the part of the body between the chest and the hips.

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Joints are the connection point between two bones that allow movement.

Spinal cord
The spinal cord is a column of nervous tissue located in the spinal column. It sends messages between the brain and the rest of the body.

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Map of Medicine: complex regional pain syndrome


Complex Regional Pain Syndrome (CRPS) is the term used to describe pain and swelling in one part of the body. CRPS usually affects the hands, feet, elbows or knees, but can affect any part of the body.

The pain may start after an injury, where the nerves have been damaged, or there may be no known cause for it to start. The pain usually gets gradually worse and may spread to other parts of the body.

There are two types of CRPS. Type 1 may not have any known cause. It used to be called Reflex Sympathetic Dystrophy (RSD), Sudecks Atrophy or Algodystrophy. Type 2 always follows an injury and used to be called causalgia.

CRPS is quite rare (an estimated 11,500 people in the UK have it) and half of all people that develop it recover within a few months.


Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

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The materials in this website are in no way intended to replace the professional medical care, advice, diagnosis or treatment of a doctor.  The website does not have answers to all problems and answers to specific problems may not apply to everyone.  If you notice medical symptoms or feel unwell, you should consult your doctor.  For further information, consult the terms and conditions.

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