Complex regional pain syndrome: symptoms, diagnosis and treatment
Complex regional pain syndrome, usually shortened to CRPS, is an uncommon pain disorder that most often affects a hand, arm, foot or leg after an injury or operation. It causes ongoing regional pain, together with a variable combination of changes in sensation, skin temperature or colour, swelling, sweating, movement, and sometimes the appearance of the skin, hair, or nails.
CRPS can be severe and disabling, but its course differs considerably between people. Some people improve substantially, while others experience persistent symptoms. Prompt assessment is useful because other medical conditions can produce similar symptoms and because early loss of movement can contribute to stiffness and declining function. There is no single diagnostic test or treatment that works for everyone.[1–5]
What does “pain disproportionate to the injury” mean?
This is clinical terminology used in the diagnostic criteria. It means that the severity, duration or distribution of pain is greater than would usually be expected during recovery from a similar injury. It does not mean that the pain is exaggerated, imagined or deliberately overstated.
WHAT IS COMPLEX REGIONAL PAIN SYNDROME?
CRPS often begins after a fracture, sprain, operation, crush injury, soft-tissue injury or nerve injury. In some people, there is no clearly identifiable trigger. The original injury may appear relatively minor, and the severity of that injury does not reliably predict who will develop CRPS or how severe it will become.
Unlike pain confined to a particular joint, muscle or nerve, CRPS pain is regional. It usually affects a broader part of a limb and is often most noticeable toward the hand or foot. People may describe burning, aching, stabbing, throbbing, electric or deeply uncomfortable pain. Light touch, clothing, temperature change or ordinary movement may become painful.
Two main types are recognised:
CRPS type I: there is no identified nerve injury that adequately explains the condition. This was previously called reflex sympathetic dystrophy.
CRPS type II: there is an identifiable nerve injury. This was previously called causalgia.
The two types have substantially overlapping symptoms and are generally managed using similar principles. The type alone does not determine how severe CRPS will be or how a person will respond to treatment.[1–3]
SYMPTOMS AND SIGNS OF CRPS
Symptoms can change from day to day and may be more obvious at some appointments than others. A limb may be warm and red at one time but cooler or paler at another. CRPS is therefore not necessarily reliably divided into fixed or predictable “stages.”
The main clinical features fall into four groups:
Sensory changes
These can include:
continuing regional pain
allodynia, where normally non-painful contact such as clothing or light touch causes pain
hyperalgesia, where a painful stimulus causes a more intense response than expected
altered sensitivity to temperature, pressure or movement.
Vasomotor changes
Changes in the regulation of blood flow may cause:
a temperature difference between limbs
red, purple, mottled or pale skin
changes in colour that fluctuate over time.
Sudomotor changes
These can include:
swelling or oedema
increased or reduced sweating
a difference in sweating between the affected and unaffected sides.
Motor/Trophic (movement and tissue) changes
These may include:
reduced range of movement
stiffness
weakness or difficulty activating the limb
tremor, muscle spasm or, less commonly, sustained abnormal posturing
changes in skin, hair or nail growth.
Weakness does not necessarily indicate that a major motor nerve has been damaged. Pain, swelling, fear of movement, altered motor control and disuse can all make a limb feel weak or difficult to control.
Symptoms may extend within the affected limb and, less commonly, appear in another limb. New symptoms elsewhere should not automatically be assumed to represent “spread.” The new area should be examined and should independently meet the diagnostic criteria before being labelled CRPS.[1–5]
WHAT CAUSES CRPS? CURRENT UNDERSTANDING
CRPS does not appear to have one single cause. Current evidence suggests that several biological and behavioural processes may interact, and the relative importance of each process probably varies across individuals.
Possible mechanisms include:
Peripheral and central sensitisation: pain-processing pathways become more responsive, so sensory information may be amplified and normally harmless input can become painful.
Inflammatory and immune signalling: inflammatory changes may contribute, particularly earlier in the condition, although research findings are inconsistent and do not provide a clinical diagnostic test.
Autonomic and small-vessel regulation: changes in the systems controlling blood flow, skin temperature and sweating may help explain colour, temperature and sweating differences.
Movement and disuse: pain, swelling, guarding and immobilisation can lead to stiffness, weakness and altered movement.
Changes in body perception and sensory-motor processing: some people experience the affected limb as unusually large, small, foreign, distorted or difficult to locate or control. Changes have been identified in brain networks involved in sensation, movement and body perception, but these findings are not present in every person and are not diagnostic.
These mechanisms remain areas of active research. Findings involving inflammation, antibodies, neuropeptides or brain imaging should not be interpreted as proving that one particular mechanism is responsible for an individual patient’s symptoms.[1,2]
IS CRPS PSYCHOLOGICAL?
CRPS is not caused simply by anxiety, depression, personality or a lack of resilience. There is no recognised “CRPS personality,” and psychological distress does not make the pain unreal.
However, severe pain, uncertainty, disrupted sleep, reduced mobility, loss of work and fear about the limb can understandably cause distress. Anxiety, low mood, post-traumatic symptoms, fear of movement and unhelpful beliefs about damage can then increase disability or make rehabilitation more difficult. These factors deserve treatment as part of comprehensive care, without implying that they caused CRPS.[1–3]
HOW IS CRPS DIAGNOSED?
There is no blood test, scan, or nerve test that can confirm CRPS on its own. Diagnosis is clinical and is usually made using the Budapest Criteria.
All four of the following requirements must be met:
There is continuing pain that is disproportionate to the usual course of any triggering injury or event.
The person reports at least one symptom in at least three of the four categories:
sensory
vasomotor
sweating or oedema
motor or trophic.
The clinician observes at least one sign in at least two of those four categories during the examination.
No other diagnosis better explains the presentation.
A symptom is something the person experiences and reports. A sign is something that is present and observed during the examination. This distinction is important because symptoms may fluctuate and may not always be visible at a particular appointment.[2,4,5]
Investigations may still be required. Depending on the presentation, these might be used to look for:
infection
a new or unhealed fracture
joint, tendon or soft-tissue disease
a focal nerve injury
arterial or venous circulation problems
a blood clot
inflammatory disease
another neurological or musculoskeletal condition.
X-rays, MRI scans and bone scans sometimes show changes associated with CRPS, but these findings are not sufficiently specific to establish the diagnosis. Normal imaging does not exclude CRPS, and an abnormal scan does not confirm it.
WHY PROMPT ASSESSMENT MATTERS
Prompt assessment is valuable, but patients should not be told that there is a precisely defined or guaranteed “window” in which CRPS can be cured. Current evidence does not support such a claim.
Earlier assessment can nevertheless help to:
identify or exclude another medical condition
ensure that the original injury is being managed appropriately
provide an understandable explanation of the symptoms
address swelling and loss of movement
begin a graded plan for restoring function
reduce unnecessary immobilisation, fear and repeated investigations.
Temporary protection or immobilisation may be necessary for some acute injuries. Once medically safe, however, prolonged guarding or complete avoidance of the limb can contribute to stiffness, weakness and loss of function. Rehabilitation should respect tissue healing and should not be forced or excessively painful.[1–3,6,7]
TREATMENT: AN INTEGRATED AND INDIVIDUALISED APPROACH
CRPS treatment usually combines education, pain management, physical rehabilitation and psychological support. Some people may also be considered for procedures.
It is important to be open about the limitations of the evidence. A large Cochrane overview found no high-certainty evidence supporting any single CRPS treatment. Many studies have included small numbers of participants, used different definitions and treatments, or had a substantial risk of bias. This does not mean that no treatment can help an individual. It means that outcomes are uncertain, responses vary and treatment should be reviewed against clearly defined goals.[6,7]
Useful goals might include:
using the hand for dressing, cooking or personal care
tolerating shoes or clothing
walking a particular distance
improving sleep
returning to driving, work or study
reducing reliance on mobility aids
participating more fully in family or social activities.
Pain intensity is relevant, but it should not be the only outcome measured. Function, sleep, emotional wellbeing, participation and treatment side effects are also important.
Physical and occupational rehabilitation
Restoring safe and useful movement is usually a central part of CRPS management. Physiotherapy and occupational therapy may address:
gentle range-of-motion exercises
gradual functional use of the limb
progressive loading or weight-bearing
hand therapy or gait retraining
swelling management
desensitisation
strength, balance and coordination
practical adaptations for home, work or self-care
planning a gradual return to valued activities.
Rehabilitation should be graded and tolerable rather than forced. A temporary increase in symptoms may occur when activity is increased, but severe or sustained deterioration should prompt reassessment and modification of the program. “Pushing through” or “boom and bust” behaviour leading to escalating pain is not the aim.
Graded motor imagery, laterality exercises and mirror therapy may be offered to some people. They are intended to address altered body perception and sensory-motor processing. Some small studies have reported benefit, but systematic reviews conclude that the overall evidence remains very uncertain. These techniques should therefore be presented as possible trials, not as proven or essential treatments.[2,6,7]
Splints, braces, or mobility aids may be useful for particular short-term goals, safety, or protection during an acute injury. Their ongoing use should be reviewed so that they do not unnecessarily reinforce disuse.
Medicines and pain relief
Pain relief may help a person sleep, move and participate in rehabilitation, but no medicine reliably treats CRPS as a whole.
A range of prescription treatments has been studied, including medicines directed at neuropathic pain, inflammation, bone metabolism and severe refractory pain. Overall evidence is limited, and many uses are outside the medicine’s specifically approved indication, so called “off-label” use. Possible benefit must therefore be balanced against adverse effects, interactions, other health conditions and the risk that medication side effects may themselves reduce activity or function.[2,6,9–12]
When a medicine is trialled, it is reasonable to agree in advance:
which symptom or functional goal is being targeted
how long the trial will continue
which adverse effects will be monitored
what improvement would justify continuing
when the medicine will be reduced or stopped if it is not useful.
Long-term opioid therapy is not routinely supported as a stand-alone strategy for CRPS. CRPS-specific trial evidence is lacking, while tolerance, dependence, sedation, constipation, hormonal effects, overdose risk and increased pain sensitivity are recognised concerns with longer-term or higher-dose opioid exposure. Any use requires individual assessment and regular medical review.[2,6]
This page intentionally does not provide drug names, doses or a treatment sequence. Those decisions require an individual medical assessment and cannot be safely determined from a general information page.
Psychological support
Psychological treatment does not imply that CRPS is imaginary or “all in the mind.” Its purpose is to help manage the substantial emotional, cognitive and behavioural effects of persistent pain.
Pain-focused psychological care may assist with:
fear of movement or reinjury
pain-related distress and catastrophising
sleep disruption
low mood or anxiety
adjusting to changes in work, family or independence
pacing activity without complete avoidance
relaxation and regulation of physiological arousal
trauma symptoms when an accident, operation or treatment experience has been distressing.
Approaches may include cognitive behavioural therapy (CBT), acceptance-based therapy (ACT), pain neuroscience education, relaxation training and graded exposure. CRPS-specific evidence for psychological therapies is limited, but psychological support is recommended as part of coordinated care when distress, avoidance or adjustment difficulties are interfering with rehabilitation.[1–3]
Sympathetic nerve blocks and radiofrequency neurotomies
Sympathetic nerve blocks involve placing local anaesthetic near sympathetic nerves. Examples include blocks directed toward the upper limb or lower limb sympathetic pathways.
These procedures have historically been used in CRPS, but the evidence remains limited and does not show reliable benefit compared with placebo or rehabilitation alone. The available studies are small, inconsistent and mostly of low or very low quality. Sympathetic blocks should therefore not be described as routinely effective, as reversing CRPS or as proving that pain is “sympathetically maintained.”[6,13]
A carefully selected patient may be offered these treatments if they are not responding to conservative management options and with the express aim of temporary pain reduction to permit more active rehabilitation. Before proceeding, there should be:
a clear treatment goal
discussion of alternatives and risks
a plan for measuring benefit
an understanding that any benefit may be partial or temporary
a plan to not repeat the procedure if it is not producing meaningful improvement.
Spinal cord and dorsal root ganglion stimulation
Neuromodulation may be considered for selected people with persistent, disabling CRPS when coordinated rehabilitation, psychological support and less invasive measures have not provided sufficient improvement.
Spinal cord stimulation and dorsal root ganglion stimulation use implanted electrical leads to modify pain signalling. A temporary trial is usually performed before permanent implantation.
Randomised studies suggest that these treatments can reduce pain in some carefully selected patients. One comparative trial found better treatment success with dorsal root ganglion stimulation than conventional spinal cord stimulation at 3 and 12 months in people with lower-limb CRPS or causalgia. However, the number and duration of high-quality studies remain limited. Longer-term spinal cord stimulation follow-up also suggests that average benefits may diminish over time.[14,15]
Neuromodulation is not a cure and restoration of normal function is not guaranteed. Possible complications include:
infection
bleeding
lead movement or breakage
equipment malfunction
unpleasant or ineffective stimulation
loss of benefit over time
the need for revision, replacement or removal
anaesthetic and surgical complications.
Suitability requires a comprehensive, multidisciplinary assessment, realistic goal-setting and informed consent. Neuromodulation should generally complement rather than replace active rehabilitation and self-management.
PROGNOSIS AND LIVING WITH CRPS
The long-term course of CRPS is variable. Many people improve substantially, and the greatest change may occur during the first year. However, persistent pain, stiffness, weakness, altered sensation and difficulty returning to work or usual activities remain significant problems for some people.
Current evidence does not allow clinicians to predict an individual outcome with certainty. Recovery may be gradual and non-linear, and different symptoms may improve at different rates.[8]
Even when pain persists, treatment may still improve:
mobility and limb use
independence
sleep
confidence with movement
work and social participation
emotional wellbeing
the ability to manage symptom fluctuations.
A long-term plan may include sustainable activity, home exercises, pacing, sleep and mood management, workplace adjustments and periodic review of medicines or procedures. The aim is not to deny the pain or simply measure pain scores, but to reduce its impact and improve the person’s ability to participate in valued activities.
Key messages for patients and families
CRPS is a recognised clinical disorder. It is not evidence of weakness, exaggeration or imagined pain.
Diagnosis is based on the Budapest Criteria and requires exclusion of a better explanation.
There is no single blood test, scan, medicine or procedure that confirms or cures CRPS.
Functional rehabilitation is usually central, but it should be graded and individually adjusted rather than forced.
Evidence for most individual treatments is limited, and responses vary.
Medicines and procedures should have clear goals, measurable outcomes and a plan for review or discontinuation.
Psychological support addresses the effects of living with pain; it does not imply that psychological factors caused the condition.
New or rapidly changing symptoms should be medically assessed rather than automatically attributed to CRPS.
General information disclaimer
This information is for general education and does not replace individual medical assessment, diagnosis or treatment. Treatment suitability, benefits and risks vary between people. Some treatments studied for CRPS may be used outside their specifically approved indications. Surgical and other invasive procedures carry risks and require individual assessment and informed consent. No treatment outcome can be guaranteed.
REFERENCES
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Ferraro MC, Cashin AG, Wand BM, Smart KM, Berryman C, Marston L, Moseley GL, McAuley JH, O’Connell NE. Interventions for treating pain and disability in adults with complex regional pain syndrome—an overview of systematic reviews. Cochrane Database Syst Rev. 2023;6:CD009416. doi:10.1002/14651858.CD009416.pub3.
Smart KM, Ferraro MC, Wand BM, O’Connell NE. Physiotherapy for pain and disability in adults with complex regional pain syndrome types I and II. Cochrane Database Syst Rev. 2022;5:CD010853. doi:10.1002/14651858.CD010853.pub3.
Johnson S, Cowell F, Gillespie S, Goebel A. Complex regional pain syndrome: what is the outcome? A systematic review of the course and impact at 12 months from symptom onset and beyond. Eur J Pain. 2022;26(6):1203–1220. doi:10.1002/ejp.1953.
Zhu H, Wen B, Xu J, Zhang Y, Xu L, Huang Y. Efficacy and safety of pharmacological treatment in patients with complex regional pain syndrome: a systematic review and meta-analysis. Pharmaceuticals. 2024;17(6):811. doi:10.3390/ph17060811.
Ferraro MC, O’Connell NE, Goebel A, et al. Efficacy and safety of bisphosphonates for complex regional pain syndrome: a systematic review and meta-analysis. Ann Intern Med. 2026;179(2):256–269. doi:10.7326/ANNALS-25-03693. The 2026 review found possible short-term pain reduction but uncertainty at other time points and an increased risk of adverse events.
Ferraro MC, Cashin AG, Visser EJ, et al. Ketamine and other NMDA receptor antagonists for chronic pain. Cochrane Database Syst Rev. 2025;8:CD015373. doi:10.1002/14651858.CD015373.pub2. The review found that adequately powered trials were still needed to determine benefits and harms.
van den Brink J, van der Spek DPC, Baart SJ, Huygen FJPM, Dirckx M. Intravenous ketamine for complex regional pain syndrome: pain outcomes and predictors of response—a systematic review and meta-analysis. J Pain. Published online 4 August 2026:106397. doi:10.1016/j.jpain.2026.106397. Most included studies had a moderate-to-high risk of bias; early pain reduction was reported, but limited longer-term data suggested that benefit diminished toward baseline.
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