Complex regional pain syndrome

21 min read

What is complex regional pain syndrome?

Complex regional pain syndrome (CRPS) is a poorly understood condition in which a person develops a persistent (chronic) burning pain in one of their limbs.

The pain usually develops after an injury – which in most cases is a minor injury – but the pain experienced is out of all proportion to what you would normally expect. For example, a person with CRPS may only strain their ankle but it can feel like a serious burn.

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.

If left untreated the pain can spread to other parts of the body too.

Read more information about the

symptoms of complex regional pain syndrome

In some cases of CRPS the pain passes after a few weeks. In others it can persist for months or even years. Some people have repeated episodes of pain followed by long stretches of remission (being pain-free).

Treating CRPS

There are three main treatment approaches for CRPS which are used in combination:

  • physical therapy, such as
    , to help improve the range of movement in the affected body part and prevent muscle wasting
  • medication, such as the
    non-steroidal anti-inflammatory drugs
    (NSAIDs) type of painkillers such as
    , to relieve pain
  • counselling
    and support to help people cope better emotionally with the impact of living with chronic pain

The sooner treatment is started after symptoms begin, the more effective it will be.

Read more information about the

treatment of complex regional pain syndrome

What causes CRPS

The cause of CRPS is unknown but the condition appears linked to an abnormal neural (involving the nervous system) response to injury.

It appears something (nobody is sure what) causes certain nerves to misfire in some way triggering pain.

CRPS could be the result of interconnected factors.

A previous theory that CRPS was a psychosomatic condition (the symptoms of pain were psychological – "all in the mind") has been disproved because research shows people with CRPS undergo very real physical changes in their nervous system.

Read more about the possible

causes of complex regional pain syndrome

Who is affected

It is hard to estimate exactly how common CRPS is as many cases may go undiagnosed or misdiagnosed.

CRPS can begin at any age, though the average age for symptoms to start is around 40. Three out of four cases occur in women.


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

The brain, spinal cord and nerves.

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).

Complex regional pain syndrome symptoms

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 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, muscles in the affected limb may begin to waste (atrophy). This usually occurs if the person affected is unwilling to use their limb due to associated pain.

Other symptoms

CRPS can cause other symptoms, including:

  • alternating changes in skin temperature – sometimes your skin may feel sweaty, other times cold and clammy
  • changes in skin colour – your skin tone may range from pale and colourless to pink, or 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 your hair and nails grow – either unusually slowly or quickly
  • swelling, pain and stiffness in the affected joints
  • increasing difficulty moving the affected body part

Stages of CRPS

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

Stage one

This 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 muscles contract tightly and painfully)
  • joint stiffness
  • rapid growth of hair and nails

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

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

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 significant 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 arm
    , can lead to type two CRPS (triggered by a more serious injury).

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

Some experts believe CRPS shouldn't be regarded as a single medical condition as there could be different conditions that all cause the same symptoms. Some of the theories about the causes of CRPS are described below.

Psychological abnormalities

A number of psychologists, including Sigmund Freud, have suggested that CRPS may be a psychological condition 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".

Sympathetic nervous system malfunction

Another theory is that CRPS is associated with a malfunction in the sympathetic nervous system.

The sympathetic nervous system is the part of the nervous system 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 hormones your body usually releases during stressful situations, as part of the "fight or flight reflex" explained above.

It is thought these hormones then activate pain receptors, which 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 causing the problem, but your body's abnormal response to it.

As the sympathetic nervous system also helps regulate blood vessels in your skin, a malfunction of this system may also account for other associated symptoms of CRPS, such as 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 to help prevent the spread of infection. This process is known as inflammation.

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 possible causes include:

  • Some people may be more susceptible to CRPS because of genetic factors.
  • If you are not using the affected limb enough, CRPS may be more likely to occur following an injury.
  • 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 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 Genetic is a term that refers to genes. Genes are the characteristics inherited from a family member. Hormones 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 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.

Complex regional pain syndrome diagnosis

There is no single test for complex regional pain syndrome (CRPS). It is usually diagnosed by ruling out other conditions that have similar symptoms.


Possible tests used to rule out other conditions are:

Tests that give a good indication that you have developed CRPS (although they can't confirm it) are described below.

  • A physical examination, where your doctor or another specialist will check for physical signs of CRPS, such as swollen joints and changes to your skin’s temperature and appearance.
  • Sweat testing, where the sweat 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, where wires are attached to your skin 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 difficult to diagnose, experts have created a checklist to assist doctors and other healthcare professionals when making a diagnosis.

A diagnosis of CRPS can be made if 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 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, mostly within hospitals.

There is also a national centre for CRPS based at the Royal National Hospital for Rheumatic Diseases in Bath. You may be advised to visit the centre once your diagnosis is confirmed so that a treatment plan can be drawn up.

An urgent referral ensures treatment can be started immediately, because the earlier treatment is started, the less likely it is that you'll have any long-term disability.


Inflammation 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. Joint Joints are the connection point between two bones that allow movement. Trauma Damage to the body’s tissues.

Complex regional pain syndrome treatment

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

Helping you cope better with the emotional impact of living with pain is also an important part of treatment.

Your care team

Due to the complex nature of CRPS, treatment is usually provided by a team of different professionals working together.

Members of your care team may include:

  • a physiotherapist – who will help you to improve your range of movement and coordination
  • an occupational therapist – who will help you improve skills needed for daily activities
  • a neurologist – a doctor who specialises in the treatment of conditions that affect the nervous system (the nerves, brain and spinal cord)
  • a psychologist – a specially trained mental health professional who can help with any associated psychological (mental) problems caused by living with a chronic (long-term), painful condition
  • a social worker – who will be able to provide information and advice about what extra help and services are available
  • a pain relief specialist – a doctor or other healthcare professional trained in pain relief


Many experts feel that

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 bones are bent out of shape)

Your physiotherapist (a healthcare professional trained in the use of physical methods to promote healing, such as massage and manipulation) will teach you a range of exercises. These are designed to 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 the treatment.

Graded motor imagery

A review of a number of different techniques used in physiotherapy found 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. Three steps to this treatment 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 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 painful). 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 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 it may be beneficial.

Occupational therapy


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

For example, if you are experiencing pain in one arm, an occupational therapist will 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 several medicines that have proved successful in treating CRPS. Your doctor or pain specialist will be able to discuss these with you.

Your treatment team will try lower-strength painkillers first, and will only use stronger painkillers if necessary.

Alternatively, a short-term course of strong painkillers may be used to enable you to start physiotherapy. Once you begin to respond to 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 often used to treat CRPS are over-the-counter (OTC) painkillers called

non-steroidal anti-inflammatory drugs
(NSAIDs), such as

People are often surprised that NSAIDs are recommended to treat severe pain. However, they have been shown to be very effective. They can also help reduce any associated swelling.

Nerve blocks

Nerve blocks are often used to provide short-term pain relief for people with CRPS. This involves injecting local anaesthetic into a group of affected nerves. This prevents 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
  • 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.


Anticonvulsants were originally designed to treat epilepsy. 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:

Avoid suddenly stopping taking gabapentin because you will experience withdrawal symptoms. If you no longer need to take it, your doctor will arrange for your dose to be slowly reduced over a period of a week.

Tricyclic antidepressants (TCAs)

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

Side effects when taking amitriptyline include:

Amitriptyline should not be taken by people with a history of heart disease.

Gabapentin and amitriptyline are not recommended if you’re pregnant unless your doctor feels that the benefits clearly outweigh the risks. There’s evidence that amitriptyline may cause harm to the baby and with gabapentin there is not enough information to say that it is safe. If you are planning to become pregnant or find out that you are pregnant whilst taking this medication/these medications, speak to your doctor and midwife as soon as possible.


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

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

There is also a risk of addiction. Your dosage will therefore be carefully monitored to reduce this risk as much as possible.

Spinal cord stimulation

Spinal cord stimulation is a possible treatment for pain caused by nerve problems (neuropathic pain).

A device is placed under your tummy or buttocks. This 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 changes to 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 removed if necessary.

A trial in people with type one CRPS found that, compared with 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 care team will discuss spinal cord stimulation with you if they think it would benefit you.

Psychological treatments

Living with a long-term, painful condition can be distressing and people with CRPS may experience anxiety and


It is important to look after your psychological wellbeing, because feelings of depression and anxiety can interfere with your physiotherapy.

Psychological therapies can also be useful in helping you 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 physiotherapy, which also helped reduce their pain symptoms.


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

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.