What is complex regional pain syndrome?

Complex regional pain syndrome (CRPS) is a chronic condition that causes persistent pain, most often in an arm or leg. Unlike typical pain after an injury, CRPS pain does not improve as expected over time and may become more severe. It can also affect the skin, muscles, joints and blood flow in the affected area.

What causes complex regional pain syndrome?

Experts are not sure of the exact causes of CRPS, but nerve damage is suspected as one of the triggers. In most cases, the condition occurs after some type of injury to the affected area. But this is not always the case.

CRPS is thought to involve a combination of:

• Abnormal nerve signaling
• Increased sensitivity of pain pathways
• Changes in the immune and inflammatory systems
• Dysfunction of the sympathetic nervous system (the body’s fight-or-flight response)

There are two types of CRPS:

• Type I (formerly reflex sympathetic dystrophy): Occurs without a confirmed nerve injury.
• Type II (causalgia): Occurs after a known nerve injury.

What are the symptoms of complex regional pain syndrome?

People who have CRPS may experience:

• Continuous burning pain in an arm, leg, hand, foot or other part of the body.
• Swelling in the affected area.
• Changes in skin temperature (warm or cool compared with the opposite limb).
• Dramatic changes in skin color (red, blue, pale or blotchy).
• Changes in skin texture (thin, shiny or sweaty).
• Decreased range of motion, stiffness or weakness.
• Changes in hair and nail growth.

How is complex regional pain syndrome diagnosed?

There is no single test to diagnose CRPS. Diagnosis is based on:

• Medical history, including previous injuries or other major health events.
• Physical examination.
• Presence of symptoms that point to CRPS.

Tests may be used to rule out other conditions or support the diagnosis. These may include:

• Autonomic testing to evaluate blood flow or sweating.
• Nerve studies.
• Imaging, such as X-rays, MRI or bone scans.
• A sympathetic nerve block to help determine if the sympathetic nervous system is causing the pain. It involves injecting an anesthetic into the nerves near the spine. If the nerve block helps the pain, a series of nerve blocks may help with ongoing relief.

How is complex regional pain syndrome treated?

There is no single cure for CRPS, but a combination of treatments can help manage symptoms and improve function. Early, active treatment is important.

Treatment may include:

• Medications:
• Pain medicines
• Antidepressants
• Antiseizure medicines
• Oral steroid medicines
• Interventional and advanced therapies:
• Sympathetic nerve blocks
• Spinal cord stimulation (a type of neuromodulation that uses mild electrical signals to modify pain signaling)
• Peripheral nerve stimulation
• Rehabilitation therapies
• Physical therapy
• Occupational therapy
• Other approaches
• Psychological support (for coping with chronic pain)
• Relaxation techniques or biofeedback

Not all treatments work for everyone, and a treatment plan is usually tailored for each person. Advanced therapies for CRPS are typically delivered by specialists with expertise in complex pain conditions.

Living with complex regional pain syndrome

Living with CRPS can be challenging, but many people improve with a coordinated treatment approach.

Helpful strategies include:

• Staying as active as possible within comfort limits.
• Following your therapy and exercise program.
• Taking medications as prescribed.
• Communicating regularly with your care team.

CRPS can also affect emotional well-being. People with CRPS may develop anxiety, depression or post-traumatic stress, all of which may worsen pain. Support and treatments are available and can be an important part of recovery. In some cases, care may include advanced therapies such as neuromodulation as part of a comprehensive, team-based treatment plan.

When should I call my doctor?

People with CRPS may benefit from evaluation at specialized pain centers with experience in advanced therapies. Contact your doctor if you experience:

• New or worsening pain or symptoms.
• Medication side effects such as drowsiness, confusion or changes in consciousness.
• Difficulty performing daily activities.

Medically reviewed by Eellan Sivanesan, M.D., June 18, 2026.