Complex regional pain syndrome !

Severe, lasting pain in an arm or leg after an injury, with swelling, colour and temperature changes and stiffness far beyond the original damage.

Updated 2026-11-01

Structures involved

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Why it happens

What it is

A chronic pain condition, usually of a limb, in which pain is disproportionate in duration or intensity to the triggering event and is accompanied by sensory, vasomotor, sweating, oedema and motor or trophic changes. It typically follows a fracture (classically of the distal radius), surgery or minor injury.

Who gets it

Occurs after a small percentage of limb fractures and surgeries, most often of the wrist. It is about three to four times more common in women and peaks around 40 to 60 years. It is a recognised cause of work disability in trauma and orthopaedic practice in Colombia.

Causes

Fractures, especially distal radius fractures
Surgery, sprains, crush injuries or casting
Nerve injury (type II)
Stroke or myocardial infarction in some cases
Occasionally no clear trigger

Risk factors

Female sex and middle age
Distal radius fracture, particularly with a tight cast or prolonged immobilisation
High pain intensity early after injury
Smoking
History of migraine, asthma or ACE inhibitor use has been associated

Pathophysiology

Several mechanisms combine: exaggerated local inflammation (neuropeptides such as substance P and CGRP), peripheral and central sensitisation, autonomic dysfunction with altered blood flow and sweating, and cortical reorganisation of the body map. Disuse and fear of movement worsen stiffness, osteoporosis and atrophy.

Classification

Type I (formerly reflex sympathetic dystrophy): no identifiable major nerve injury
Type II (formerly causalgia): follows a confirmed peripheral nerve injury
Warm (acute) and cold (chronic) clinical phenotypes

Symptoms and signs

Burning or throbbing pain out of proportion to the injury, with allodynia and hyperalgesia
Swelling of the hand or foot
Changes in skin colour (red, purple or pale) and temperature compared with the other limb
Abnormal sweating
Stiffness, weakness, tremor and reduced range of movement
Changes in hair and nail growth and shiny, thin skin

Diagnosis

Clinical: A clinical diagnosis using the Budapest criteria: continuing pain disproportionate to the inciting event, symptoms in at least three of four categories (sensory, vasomotor, sudomotor/oedema, motor/trophic), signs in at least two categories at examination, and no other diagnosis that better explains them.
Tests: No specific test. Basic blood tests (blood count, ESR, CRP) to exclude infection or inflammatory arthritis; nerve conduction studies if nerve injury is suspected.
Imaging: Plain radiographs may show patchy periarticular osteopenia; a three-phase bone scan or MRI can support the diagnosis or exclude other causes, but they are not required.

Differential diagnosis

Cellulitis, septic arthritis or osteomyelitis
Deep vein thrombosis
Non-union or malunion of a fracture
Peripheral nerve entrapment such as carpal tunnel syndrome
Inflammatory arthritis
Raynaud phenomenon or vascular insufficiency

Goal of treatment

Restore use of the limb and reduce pain early, before stiffness and atrophy become permanent, with an active, multidisciplinary approach.

Treatment

Rehabilitation: Physical and occupational therapy are the core: graded activity, desensitisation, mirror therapy and graded motor imagery, encouraging use of the limb.
Medical: Medicines to support rehabilitation: NSAIDs, a short course of oral corticosteroids in early warm CRPS, bisphosphonates, gabapentinoids, and tricyclic or SNRI antidepressants for neuropathic pain.
Procedure: Selected refractory cases: sympathetic nerve blocks or spinal cord stimulation by a pain specialist.
Conservative: Psychological support (cognitive behavioural therapy, pain education) and treatment of anxiety, depression and sleep problems.
Follow-up: Regular assessment of pain, swelling, range of movement and function; after fractures, check cast fit and teach finger exercises, which nurses reinforce.

Complications

Permanent stiffness, contractures and muscle atrophy
Disuse osteoporosis
Spread of symptoms to other limbs (uncommon)
Chronic disability, depression and anxiety
Skin ulcers and infection in severe cases

Prognosis

Many patients improve within one to two years, especially with early active rehabilitation, but a sizeable minority keep chronic pain and disability. Outcome is worse with long delays in diagnosis and in the cold phenotype.

Prevention

Early mobilisation of fingers and joints after fractures and surgery, and avoiding overly tight casts
Good early pain control after injury; vitamin C after wrist fracture has been studied with mixed evidence

Test yourself

Think of the answer, then tap the question to see it.

Which fracture classically precedes complex regional pain syndrome?

Distal radius fracture.

What distinguishes CRPS type II from type I?

Type II follows a confirmed peripheral nerve injury; type I has no major nerve lesion.

Which criteria are used for diagnosis?

The Budapest criteria.

What is the cornerstone of treatment?

Early physical and occupational therapy that restores limb use, supported by pain medicines and psychological care.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Complex regional pain syndrome (MedlinePlus (U.S. National Library of Medicine), 2026).

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Representative model, for educational purposes only.

Radius highlighted on the Durgical 3D model