Reflex sympathetic dystrophy (RSD) is a chronic pain condition that causes intense, burning pain in a limb, usually after an injury or surgery. The pain is far out of proportion to the original injury and comes with visible changes like swelling, skin color shifts, and temperature differences in the affected area. Since 1993, the medical community has officially called this condition complex regional pain syndrome type 1 (CRPS-1), though many people still know it by its older name.
Why the Name Changed
The term “reflex sympathetic dystrophy” was the standard name through most of the 20th century, but it implied a specific cause (the sympathetic nervous system) that turned out to be only part of the picture. In 1993, the International Association for the Study of Pain introduced “complex regional pain syndrome” as a more neutral replacement that didn’t assume a single mechanism.
Under the new system, CRPS is split into two types. Type 1 (formerly RSD) develops without confirmed nerve damage. Type 2 (formerly called causalgia) involves a verified nerve injury. In practice, though, research has found no significant differences in signs or symptoms between the two types. There is now evidence that even Type 1 involves neurological changes at a microscopic level, which has led some researchers to question whether the distinction is meaningful at all.
Who Gets It and What Triggers It
CRPS affects roughly 26 per 100,000 people each year, and women develop it at least three times more often than men. An analysis of over 1,000 patients found the most common triggers were fractures (42%), blunt injuries like sprains (21%), surgery (12%), and carpal tunnel syndrome (7%). About 7% of cases had no identifiable cause at all.
In children, CRPS-1 is more common in girls and typically diagnosed around age 12. Triggers in kids tend to be milder, often something as routine as an ankle sprain.
What Happens in the Body
RSD involves several overlapping problems in the nervous system. After an injury, the body’s normal inflammatory response essentially gets stuck. Nerves in the affected area release inflammatory signals that don’t shut off the way they should, creating persistent swelling, warmth, and pain.
At the same time, the spinal cord and brain become hypersensitive to pain signals from the affected limb, a process called central sensitization. Neurons that transmit pain become more excitable while the brain’s ability to dampen those signals weakens. The sympathetic nervous system, which normally manages involuntary functions like blood flow and sweating, also becomes dysregulated. This hyperactivity fuels more inflammation and sensitization, creating a self-reinforcing cycle that can persist long after the original injury has healed.
Symptoms and How They Progress
The hallmark of RSD is pain that doesn’t match the injury. A minor sprain might produce severe, constant burning that lasts months. Beyond pain, the condition produces a distinctive cluster of symptoms across four categories: sensory changes, blood flow problems, sweating and swelling, and movement difficulties.
Doctors typically describe three stages of progression, though not everyone moves through them in a neat sequence.
Stage 1: Acute (Up to 3 Months)
Burning pain and extreme sensitivity to touch appear first. The affected limb often looks red, feels warm, and swells noticeably. Joints stiffen. Hair and nails on the limb may grow faster than normal, and you might notice unusual sweating in the area.
Stage 2: Dystrophic (3 to 12 Months)
Stiffness worsens and sensitivity to touch intensifies. The swelling may become harder and more persistent. Pain can spread beyond the original site.
Stage 3: Atrophic (After 1 Year)
The skin becomes pale, dry, shiny, and tightly stretched. Muscle wasting and joint contractures can make the limb increasingly difficult to move. Pain may actually decrease at this point, but the physical changes can become permanent. In some cases, symptoms spread to other parts of the body.
How It Is Diagnosed
There is no single blood test or imaging scan that confirms RSD. Diagnosis relies on a clinical checklist known as the Budapest criteria, which requires four things.
First, you must have ongoing pain that is disproportionate to whatever triggered it. Second, you need to report at least one symptom in each of four categories: heightened pain sensitivity or pain from light touch (sensory), skin color or temperature changes (vasomotor), swelling or sweating changes (sudomotor), and decreased movement, weakness, tremor, or changes to hair, nails, or skin (motor/trophic). Third, a doctor must observe at least one visible sign in two or more of those same categories during an exam. Fourth, no other diagnosis better explains the findings. Temperature differences of more than 1°C between the affected and unaffected limb are one measurable sign doctors look for.
Treatment Approaches
Physical and occupational therapy is considered the foundation of CRPS treatment. The goal is to gradually restore movement and function in the affected limb, even when pain makes this difficult. Therapy typically starts gently and increases in intensity as tolerance improves. In children, physical therapy alone often produces good results, with most improving within six to eight months.
For medications, bone-strengthening drugs called bisphosphonates have the strongest evidence base. Clinical trials have shown significant improvements in pain scores and quality of life with intravenous bisphosphonate treatment. Nerve-calming medications like gabapentin and pregabalin are also used, though the evidence supporting them specifically for CRPS is more limited than for other nerve pain conditions.
Addressing mental health is a critical and often overlooked part of treatment. About half of CRPS patients have a co-occurring psychiatric condition, and roughly 16% are diagnosed with depressive disorders. Depression and anxiety don’t just make the experience of pain worse. Treating them has a direct pain-relieving effect, and managing the nerve pain itself helps improve mood in return. Psychological support through therapy or medication meaningfully improves overall outcomes.
When Standard Treatment Isn’t Enough
For people whose pain doesn’t respond to therapy and medications, spinal cord stimulation (SCS) is one of the more studied options. A small device delivers mild electrical pulses to the spinal cord, interrupting pain signals before they reach the brain. In clinical trials, about 57% of CRPS patients reported significant benefits at two years, and 95% of those with implants said they would choose the treatment again. At five years, roughly 35% still met strict success criteria.
A newer technique called dorsal root ganglion stimulation targets pain signals more precisely. In a head-to-head trial of 152 patients, 81% in the dorsal root ganglion group achieved treatment success at three months compared to 56% in the standard spinal cord stimulation group.
Outlook and Recovery
Early treatment makes a significant difference. About 80% of patients recover within the first 18 months of diagnosis when they receive a combination of pain management, physical rehabilitation, education, and psychological support. The longer symptoms persist before treatment begins, the harder the condition becomes to reverse, particularly once atrophic changes set in.
Children and teenagers generally have better outcomes than adults and are more likely to achieve full recovery. Healthy older adults with good circulation and nutrition also tend to respond well. Some children do experience recurring symptoms and need to restart therapy, and a smaller number continue to have pain into adulthood. For adults with chronic CRPS that doesn’t fully resolve, the goal shifts toward maximizing function and quality of life through ongoing multidisciplinary care.