Consultant in Pain Medicine

Complex Regional Pain Syndrome



What is
Complex Regional
Pain Syndrome?

Complex regional pain syndrome (CRPS) is a distressing condition often causing severe pain that can feel relentless to the person experiencing it. 

It will typically affect a single limb, e.g. an arm or lower leg, and it may follow from trauma that has happened to that limb. It’s as if the injury has passed, but the pain persists, and is magnified and out of proportion to the severity of the initial injury. 

 Sometimes CRPS is trigged by surgery, and very occasionally by a shingles infection, or a joint strain, heart attack or stroke.

Over the years, Complex Regional Pain syndrome has had different names, including Reflex Sympathetic Dystrophy (RSD), and Sudeck’s atrophy, but now the medical community refers to it as CRPS.  

These days, CRPS is more often classified as “Acute”, usually in the first 6 or 12 months of onset, later becoming “Chronic”, and much more difficult treat. So, it is important to see a specialist to have it diagnosed and treated as soon as possible.

CRPS can affect any one at any age, but it appears to be more common from early adulthood, and women are affected more than men. It is relatively uncommon, and we don’t entirely understand why it happens in some people, but not others. 

Because it’s an uncommon condition, it may not always be recognised by doctors, and this may lead to a delay in treatment, or the wrong treatment being offered.

If you have severe pain in a limb, and are struggling to get the care you need, I’m here to help.

What are the symptoms of Chronic Regional Pain Syndrome (CRPS)?

  • The most distressing symptom that people with CRPS experience is pain. This is usually in an arm or a leg, and spreads well beyond the area of the injury or operation. Sometimes it can spread to other areas of the body.

  • The pain is often continuous, and the limb may become very sensitive indeed to light touch (“allodynia”). Even a light touch to the skin may feel very severe in terms of the level of the pain, and the pain may have a burning quality to it. The skin may also become very sensitised to the cold.

  • Skin changes are very common in CRPS. The skin may change colour, and become blotchy or red, or white or purple, often changing several times during the day. The limb may feel cooler or hotter than the skin temperature of other areas of the body, again changing throughout the day.

  • The skin may become thinned and tight and shiny or rather sweaty. Hair and nail growth may also be affected. Usually, the limb becomes swollen, and its function decreases. The palm of the hand, or the soul of the foot can often become excessively sweaty.
  • Often the arm or the leg will become stiffer and difficult to move, and the muscles may waste as function decreases.

  • Movement can feel awkward or jerky, and the limb may feel ‘strange’ to the person affected by CPRS, and the posture of the limb may become altered and fixed.

  • Some people may also report visual symptoms and ‘brain fog’ , and it’s very common for people to feel anxious, or experience depression as a consequence of their CRPS.

  • CRPS can also lead to reduced bone mineral density, bony changes in the joints of the fingers, and local osteoporosis of the bone.

  • An injury to the limb is typically the trigger for the CRPS, and this may be a relatively minor injury, such as an ankle sprain. Sometimes surgery sets it off. When we look at timelines for the onset of CRPS, the symptoms often arise around 4-6 weeks after the injury.

What causes Complex Regional Pain Syndrome (CRPS)?

  • We don’t entirely understand what causes CRPS, but it’s believed that there may be many causes which bring about a dysfunction occurring in the central and peripheral nervous systems.

  • CRPS is often precipitated by trauma or surgery, as well as the limb immobilisation which may follow these events.

  • It’s thought that in CRPS, inflammatory molecules and neuropeptides are released from peripheral nerves. Pain-sensing nerve fibres in the spinal cord become very stimulated (a process known as central sensitisation) and this produces a painful response to what would normally be a non-painful stimulus (such as light touch).  

  • The release of neuropeptides makes fine blood in the tissues ‘leaky’, causing the tissue swelling, and vasodilation (the engorgement of blood vessels) creates skin colour changes.
  • Interestingly, we know that CRPS also has an effect on the brain. In our brains, the sensing of our body parts exists in a kind of map, known as a somatopic map, in an area of the brain called the somatosensory cortex.

  • If we use the analogy of an arm or leg being represented as a continent on the map, in people who have CRPS, the continent corresponding to the affected limb becomes diminished in size when compared to the continent size of the unaffected limb.

  • When CRPS is successfully treated, the continent representing the CRPS arm or leg in the somatopic map, returns to its normal size.

  • People with CRPS also have a reduced ability to recognise left and right sides of their bodies.

How is Complex Regional Pain Syndrome (CRPS) diagnosed?

CRPS is a diagnosis that’s reached after careful history taking and examination.

Sometimes we may need to carry out blood tests or an MRI scan to rule out other conditions (such as autoimmune conditions or arthritis).

It’s important to get an early, accurate diagnosis of CRPS, as early treatment leads to a better outcome.


As doctors, we follow a set of criteria (known as the Budapest criteria) when making a diagnosis of CRPS.

These include looking at whether the person is experiencing hypersensitivity to touch, skin colour and temperature changes, swelling and sweating of the affected limb, and poor movement and function of the limb. 

Sometimes, a special isotope scan can help us diagnose CRPS.


Man with CRPS in pain

How is Complex Regional Pain Syndrome (CRPS) treated?

Physiotherapy and Occupational Therapy

These are the mainstay of treating people who have CRPS, and it’s a journey of improving mobility and function of the affected limb, whilst empowering the individual with self-management strategies to cope with their CRPS.

It is extremely important that the physio or occupational therapist fully understands about the brain and nervous system changes of CRPS. They must always avoid painful manipulation of the affected limb, because this can flair the condition up. 

The specialist physiotherapist will realise that in CRPS special visual and manual exercises are required to reunite the changes that happened in the nervous system so that the connections between brain and the affected limb can take place, allowing normal movement again, and the settling of inflammation. 

Often, your therapist may recommend ‘graded image therapy’, which is a way of retraining the brain’s connections with the affected limb. Acupuncture or TENS machine (transcutaneous electrical nerve stimulation) can help to reduce pain during and around treatment. Desensitisation training is a technique to normalise how the affected limb feels when it is touched. The person frequently touches the skin of the affected limb with different fabrics (e.g., silk and wool), and as this becomes more tolerated light pressure can be applied.

As a pain doctor specialising in CRPS, I am extremely careful about which physiotherapist I chose to treat my patients, to make sure those colleagues possess these special skills and understandings.

Physiotherapy is also important, later on, to muscle strength and mobility.   Hydrotherapy can also be very helpful.

Left-right discrimination retraining

In people with CRPS, their ability to identify left from right becomes poorer and slower, and the worse their level of pain, the worse their left-right issue becomes. The ability to determine left from right can be retrained using apps; it’s like playing a visual game of correctly naming whether a body part is on the left side of the body, or the right. As with all skills, it takes time, practice, and a bit of patience. Left-right retraining is the first stage in the rehab process.

Explicit motor imagery

This is a process of visualising moving, without actually moving your body. In the human brain we have many neurones (nerve cells), called mirror neurones. These fire if we’re thinking about making a movement, (e.g. as in sport, when you might be ‘psyching’ yourself up to take that free kick or golf swing). They can also fire if we’re watching other people move.

In people who have CRPS, explicit motor imagery can harness the activity of the mirror cells to exercise their brains, rehearsing normal movement of the affected limb.  In explicit motor imagery, the person visualises themselves performing a movement, and sense what that movement feels like (whilst keeping the limb still). This can be practised, and the movements made more complex over time.

Graded Image Therapy

Mirror box therapy

Mirror therapy

Physiotherapists will sometimes also suggest mirror work.

This kind of therapy first came about to treat patients with phantom limb pain, and it can be very useful for patients suffering from CRPS. In CRPS, during movement, sensory feedback from the affected limb becomes disturbed. Mirror therapy helps to ‘rewire’ the brain, by enabling it to ‘see’ the affected limb moving normally and without pain.

In mirror therapy, the affected limb is hidden behind a mirror, and the mirror reflects the image of the normal limb. When looking at the normal limb alongside the reflected image, the brain ‘sees’ the two limbs positioned side by side, and it perceives the reflection in the mirror as being the affected limb. The person gently moves their unaffected limb, whilst watching the reflected limb in the mirror.

In this visual illusion, it appears that the affected limb is moving normally. Initially the person may keep the painful limb still, but as therapy progresses, they will be encouraged to make the same movements as the normal limb, with their affected limb, whilst continuing to look in the mirror.

If you’re struggling with CRPS, or if you have severe pain, get in touch. I’m here to help.