Complex Regional Pain Syndrome (CRPS) is an uncommon but important pain condition, usually developing after injury or surgery and affecting a limb.

For clinicians who do not see CRPS regularly, it can be difficult to recognise. The presentation may initially resemble an unusually painful or slow recovery from injury. Conversely, severe persistent pain following trauma is sometimes labelled CRPS when the diagnostic criteria are not actually met.

Neither is helpful.

CRPS remains a clinical diagnosis. There is no single blood test, scan or investigation that confirms it. Recognition depends on identifying the characteristic combination of disproportionate regional pain alongside sensory, vasomotor, sudomotor/oedema and motor or trophic changes.

Perhaps most importantly, when CRPS is suspected, management should begin promptly rather than waiting for every diagnostic uncertainty to disappear.

When should we think about CRPS?

CRPS most commonly follows an injury, fracture or operation, although the precipitating event can sometimes be relatively minor.

Pain persists beyond what would ordinarily be expected and is typically regional rather than confined to the territory of a single peripheral nerve.

Patients may describe burning, aching, stabbing or electric pain. The affected area can become extraordinarily sensitive. Clothing, bedding or light touch may be difficult to tolerate.

But pain alone does not diagnose CRPS.

Other features may include swelling, altered sweating, changes in skin colour or temperature, stiffness, weakness, tremor, reduced movement and changes to hair, skin or nails.

These features can fluctuate over time, which is one reason the diagnosis may not be immediately apparent.

The Budapest criteria

The Budapest clinical diagnostic criteria provide a structured framework for diagnosing CRPS.

There should be continuing pain disproportionate to the inciting event.

The patient must report symptoms across at least three of four categories:

• sensory;

• vasomotor;

• sudomotor/oedema;

• motor/trophic.

At assessment, signs must be demonstrated in at least two of those four categories.

Finally, there should be no other diagnosis that better explains the presentation.

That last criterion is particularly important.

The Budapest criteria should support clinical reasoning rather than replace it.

What else could it be?

Several conditions can produce elements of a CRPS-like presentation.

Following injury or surgery, infection, vascular problems, inflammatory disease, mechanical complications and peripheral nerve injury may all need consideration depending on the circumstances.

Neuropathic pain can produce severe allodynia and sensory disturbance without fulfilling the criteria for CRPS.

Similarly, swelling, discolouration or temperature differences in isolation are not diagnostic.

The question is therefore not simply:

“Could this be CRPS?”

but also:

“Is there another explanation for these findings that we need to identify?”

CRPS I and CRPS II

CRPS has traditionally been divided into two types.

CRPS I occurs without an identified major peripheral nerve injury.

CRPS II occurs in association with a demonstrable nerve injury and was historically referred to as causalgia.

In practice, the immediate management principles overlap considerably. Establishing the presence of a significant nerve injury may nevertheless influence investigation, prognosis and treatment.

Early management matters

Once CRPS is suspected, one of the priorities is to prevent the affected limb becoming progressively less used.

This can be challenging.

Movement hurts. Touch may hurt. Patients are understandably frightened of making things worse, and repeated painful attempts at rehabilitation can further reduce confidence.

Simply telling somebody that they need to “push through the pain” is rarely helpful.

Instead, rehabilitation needs to recognise both the importance of restoring function and the sensitivity of the affected nervous system.

Early involvement of physiotherapy or occupational therapy with experience in CRPS can therefore be particularly valuable.

The aim is usually progressive restoration of movement, function and normal sensory experience, paced according to the individual rather than dictated by a rigid exercise prescription.

Pain relief should support rehabilitation

Medication may have a role, particularly where neuropathic features are prominent, although responses are variable and adverse effects can limit treatment.

The purpose of analgesic treatment should ideally be considered in functional terms.

Can we make the limb easier to touch?

Can the patient sleep better?

Can they tolerate physiotherapy?

Can they begin using the hand or foot more normally?

A reduction in a numerical pain score is useful, but it is not the only measure of progress.

What about bisphosphonates, steroids and other treatments?

A number of pharmacological treatments have been studied in CRPS, including bisphosphonates and corticosteroids, particularly in relatively early disease.

Evidence and recommendations vary according to the stage and phenotype of CRPS, and these treatments are not appropriate for every patient.

This is an area where early specialist assessment can be useful, particularly when symptoms are evolving rapidly or function is deteriorating.

More complex interventions — including sympathetic blocks, neuromodulation and other specialist pain procedures — may have a role in selected patients, but they should sit within a wider rehabilitation strategy rather than replacing it.

The nervous system is involved — but language matters

CRPS involves abnormalities in sensory processing alongside autonomic, inflammatory and motor changes. Central nervous system mechanisms may become increasingly important as symptoms persist.

Explaining this can help patients understand why the affected limb may feel dramatically different even after the original tissue injury has healed.

But language needs care.

Telling somebody that their nervous system has become “overprotective” may be useful for some patients. For others it can sound as though their symptoms are being reduced to anxiety, fear or an erroneous brain response.

The physical changes associated with CRPS are real.

Pain education should therefore add to the explanation rather than replace the clinical diagnosis.

Avoiding immobilisation — without blaming the patient

Reduced movement can contribute to stiffness, weakness, altered body perception and further loss of function.

But patients do not stop using a limb because they lack motivation.

They stop because using it can be extraordinarily painful.

That distinction matters.

The therapeutic task is to find ways of making movement possible again — through appropriate analgesia, desensitisation, graded rehabilitation, psychological support where helpful and, occasionally, specialist intervention.

Progress may initially be measured in very small changes.

Those changes still matter.

Psychological support is part of treatment, not an explanation for CRPS

Living with severe, unpredictable pain and losing the normal use of a limb can be frightening.

Anxiety, low mood, sleep disturbance, loss of work and changes in identity or relationships are understandable consequences.

Psychological approaches can help patients manage threat, distress and fear of movement and can support rehabilitation.

Their involvement does not imply that CRPS is psychological in origin.

This distinction should be made explicit.

What should trigger referral?

Early specialist advice is worth considering when CRPS is suspected, particularly where pain is severe, function is deteriorating or diagnostic uncertainty is delaying rehabilitation.

Referral does not mean that the patient necessarily needs an invasive pain procedure.

Often the most valuable contribution of specialist assessment is to confirm—or occasionally reconsider—the diagnosis, help explain what is happening, optimise symptom management and coordinate rehabilitation.

For established CRPS, multidisciplinary input becomes increasingly important.

A hopeful diagnosis

CRPS has acquired a frightening reputation.

Patients sometimes arrive having read accounts of relentless progression, permanent disability or even amputation. Understandably, this can generate enormous fear.

We should not minimise CRPS. It can be profoundly disabling and some people experience persistent symptoms.

But neither should we present the diagnosis as inevitably catastrophic.

Many patients improve, particularly when the condition is recognised and treatment supports progressive restoration of function.

The conversation at diagnosis therefore matters.

We can acknowledge the seriousness of the condition while also communicating that recovery and meaningful improvement are possible.

Bringing the pieces together

Good CRPS management rarely rests on a single treatment.

It involves recognising the clinical syndrome, excluding important alternative explanations, controlling symptoms sufficiently to enable activity, restoring movement and function, addressing the wider consequences of persistent pain and escalating to specialist treatments when appropriate.

Perhaps the most useful early principles are relatively simple:

recognise it, explain it carefully, manage the pain and keep the person moving.

For clinicians

Wye Sanctuary welcomes referrals and self-referrals for assessment of suspected or established Complex Regional Pain Syndrome, including patients where the diagnosis remains uncertain or pain is interfering with rehabilitation.

Assessment focuses on confirming the clinical phenotype, considering alternative diagnoses and developing an individual management plan. Where possible, we work collaboratively with the patient's existing physiotherapist, occupational therapist and other treating clinicians.

This article is intended for general professional education and does not replace individual clinical assessment or applicable national and local guidance.