Complex Regional Pain Syndrome (CRPS)

Quick answer

Complex Regional Pain Syndrome (CRPS) is a chronic pain disorder in which the pain is out of proportion to whatever injury triggered it. It usually develops after an injury, sometimes a minor one, and the pain is often described as burning, deep, and unrelenting. The affected limb develops characteristic changes: swelling, skin color changes, temperature differences, and exquisite sensitivity to touch. The condition is poorly understood, but early recognition and aggressive multidisciplinary treatment offer the best outcomes.

The two types

• CRPS Type 1: formerly “reflex sympathetic dystrophy (RSD).” No identifiable nerve injury. About 90% of cases.
• CRPS Type 2: formerly “causalgia.” A specific nerve injury can be identified.

The treatment is broadly similar; the distinction is mostly historical.

How to recognize it

The hallmark is pain that doesn’t fit the injury. A patient who sprained an ankle or had minor foot surgery six weeks ago should be improving. With CRPS, they’re dramatically worse, sometimes unable to tolerate a sock, a sheet brushing the foot, or even air movement.

Typical features:

Pain

• Burning, deep, throbbing quality
• Spontaneous: present even without movement or touch
• Allodynia: light touch (clothing, water, breeze) causes severe pain
• Hyperalgesia: even minor pressure causes disproportionate pain

Skin and tissue changes

• Swelling of the affected foot
• Color changes: red, blue, mottled, or pale
• Temperature differences: warmer or colder than the other foot
• Sweating changes: increased or decreased
• Skin texture changes: shiny, thin, or thickened skin
• Hair and nail changes: increased or decreased growth

Motor changes

• Stiffness
• Weakness
• Tremor
• Reluctance to move the limb
• Eventually, contractures and atrophy if untreated

Pattern

• Symptoms typically start in one location (often where the injury was) and may spread to involve the entire foot or beyond
• Symptoms don’t follow a single nerve distribution; they spread regionally

Why this happens

CRPS isn’t fully understood. Several mechanisms are thought to contribute:

• Peripheral nerve sensitization: local nerves become hyperactive
• Central nervous system changes: the spinal cord and brain amplify pain signals (central sensitization)
• Sympathetic nervous system dysfunction: explains the color and temperature changes
• Inflammatory mediators in tissue
• Genetic and immune factors in some patients

The condition is most often triggered by:

• Fractures: particularly of the wrist, ankle, or foot
• Surgery: even routine procedures
• Sprains and strains
• Casts or immobilization: sometimes from prolonged immobilization itself
• Minor procedures: injections, biopsies, blood draws

There’s no clear way to predict who will develop CRPS after a given injury.

Diagnosis

There’s no single confirmatory test, diagnosis is clinical, using the Budapest Criteria. A patient must have:

1. Continuing pain disproportionate to any inciting event
2. At least one symptom in three of four categories (sensory, vasomotor, sudomotor/edema, motor/trophic)
3. At least one sign at the time of evaluation in two of four categories
4. No other diagnosis that better explains the symptoms

Supporting tests sometimes used:

• Bone scan: may show changes in early CRPS
• MRI: for excluding other diagnoses
• Thermography: documents temperature differences
• Nerve conduction studies: for suspected CRPS Type 2

Treatment

CRPS treatment is multidisciplinary and works best when started early.

Cornerstone: physical and occupational therapy

This is the most important component:

• Desensitization: gradual, progressive exposure to touch, temperature, textures
• Range of motion exercises: preventing stiffness and contracture
• Weight-bearing progression: slowly returning normal use to the limb
• Mirror therapy: using a mirror to “trick” the brain into seeing normal limb movement, reducing pain
• Graded motor imagery: mental practice of movement
• Functional restoration

Avoiding immobilization is critical, the longer the limb is “guarded,” the more entrenched the pain becomes.

Medications

• Neuropathic pain medications: gabapentin, pregabalin, duloxetine, amitriptyline
• NSAIDs for inflammation
• Bisphosphonates: some evidence for early CRPS
• Topical medications: lidocaine patches, capsaicin
• Vitamin C: sometimes used after wrist or foot surgery to reduce CRPS risk
• Opioids: generally limited; not very effective for neuropathic pain and carry their own risks

Interventional treatments

• Sympathetic nerve blocks: local anesthetic blocks of the sympathetic ganglia (lumbar sympathetic block for foot CRPS). Both diagnostic and therapeutic.
• Spinal cord stimulators: for refractory cases
• Dorsal root ganglion stimulators: newer option
• Intrathecal medication pumps: for severe refractory cases
• Ketamine infusions: used in specialty centers

Psychological support

CRPS has a significant psychological burden, and psychological care is part of best-practice treatment:

• Cognitive-behavioral therapy: coping strategies, pain management
• Treatment of associated depression and anxiety: common in chronic pain
• Support groups: RSDSA and similar organizations

Outlook

CRPS outcomes are highly variable. Some patterns:

• Early diagnosis and treatment: best outcomes; many cases resolve or substantially improve within a year
• Delayed treatment: much harder to reverse; may become permanent
• Most patients improve with multidisciplinary care, though “complete cure” is uncommon
• A meaningful minority have persistent symptoms despite treatment

The condition can be life-altering, and matching the patient with experienced multidisciplinary care is critical.

Bottom line

CRPS is the diagnosis that should be considered when a foot injury, even a minor one, causes pain dramatically out of proportion to the injury, with skin changes, swelling, and exquisite sensitivity. Early, aggressive multidisciplinary treatment, anchored in physical therapy and including medications, blocks, and psychological support, gives the best chance of recovery. Time matters: the longer CRPS persists, the harder it is to reverse, so early referral to a pain specialist is one of the most important steps.