RSD, or reflex sympathetic dystrophy, is a chronic pain condition that causes intense burning pain, swelling, and skin changes, usually in an arm or leg after an injury. The medical community officially renamed it Complex Regional Pain Syndrome Type I (CRPS I) in 1993, so you’ll see both terms used. It affects roughly 26 people per 100,000 each year, with women developing it more than three times as often as men.
Why the Name Changed
The term “reflex sympathetic dystrophy” was first used by Evans in 1946, but by the early 1990s, researchers recognized it was misleading. The name implied the condition was driven entirely by the sympathetic nervous system, which turned out to be an incomplete picture. At a 1993 consensus meeting, specialists agreed to replace it with “complex regional pain syndrome” to better reflect the condition’s multiple overlapping mechanisms. CRPS Type I is what was formerly called RSD, developing after trauma without major nerve damage. CRPS Type II, previously called causalgia (a term dating back to the American Civil War), involves confirmed nerve injury.
What Causes It
RSD most often develops after a physical injury, and fractures are the single most common trigger, accounting for about 44% of cases. It can also follow surgery, sprains, or even minor bruising. The upper extremities are affected more frequently than the lower ones, and postmenopausal women appear to face the highest risk, with peak incidence in women between ages 61 and 70.
The condition is not fully understood, but the current view is that multiple systems malfunction at once. After the initial injury, nerve fibers in the damaged area release inflammatory substances that lower the threshold for pain signals. Essentially, nerves that would normally require a strong stimulus to fire start responding to gentle touch or mild temperature changes. At the same time, the sympathetic nervous system (the network that controls blood flow, sweating, and temperature regulation) behaves abnormally. In the early phase, sympathetic activity actually decreases in the affected limb, which triggers the body to ramp up the number of receptors sensitive to stress hormones. The result is that even normal levels of those hormones can cause excessive blood vessel constriction, temperature swings, and pain. Notably, this sympathetic dysfunction isn’t confined to the injured limb. Studies have found changes in unaffected limbs too, suggesting a broader nervous system disruption.
On top of all this, the brain itself changes. The areas responsible for processing sensation from the affected limb undergo reorganization, which can amplify and distort pain signals long after the original injury has healed. This combination of peripheral inflammation, autonomic dysfunction, and central nervous system rewiring is what makes RSD so difficult to treat.
How It Feels and What It Looks Like
The hallmark symptom is pain that seems wildly out of proportion to whatever caused it. A minor fracture or a small surgical incision produces burning, throbbing pain that doesn’t fade as the injury heals. Two specific types of heightened sensitivity are characteristic: an exaggerated response to things that should only hurt a little (like a pinprick feeling excruciating) and pain triggered by things that shouldn’t hurt at all, such as a light breeze, clothing touching the skin, or a gentle handshake.
Beyond pain, the affected limb often looks visibly different. Skin color can shift between red, blue, and pale white, sometimes within the same day. The limb may feel noticeably warmer or cooler than the other side, with temperature differences exceeding 1°C. Swelling is common, and sweating patterns change: the affected area may sweat excessively or not at all. Over time, the skin, hair, and nails can change texture. Hair may grow faster or thinner, nails may become ridged or brittle, and skin can become shiny or thin. Muscle weakness, tremors, and reduced range of motion often develop, making it difficult to use the limb normally.
How It’s Diagnosed
There is no single blood test or imaging scan that confirms RSD. Diagnosis relies on the Budapest Criteria, a clinical framework that requires all of the following:
- Ongoing pain disproportionate to the triggering event
- Symptoms reported in all four categories: heightened pain sensitivity, temperature or color changes in the skin, swelling or sweating abnormalities, and motor problems like weakness, tremor, or changes to hair, nails, or skin
- Visible signs at the time of examination in at least two of those four categories
- No other diagnosis that better explains the symptoms
The requirement for both patient-reported symptoms across all four categories and clinician-observed signs in at least two helps reduce misdiagnosis. Still, RSD is frequently diagnosed late because its early symptoms can mimic normal post-injury inflammation.
Treatment Approaches
There is no single gold-standard treatment for RSD. Management typically combines medication, physical therapy, and sometimes interventional procedures, with the mix tailored to the individual.
Traditional anti-inflammatory medications and corticosteroids have largely fallen out of favor. Recent evidence shows limited benefit from standard anti-inflammatories, and because RSD is a chronic condition, long-term corticosteroid use carries too many side effects to be practical. Instead, medications originally developed for nerve pain and seizures are now the go-to options, with gabapentin being one of the most commonly prescribed due to its relatively mild side effect profile. Certain antidepressants that also dampen nerve pain signaling are frequently used as well. Bone-strengthening medications called bisphosphonates have also shown benefit, likely because they reduce the inflammatory bone changes that can accompany the condition.
For people who don’t respond to medication alone, nerve blocks (injections that temporarily interrupt pain signals) and spinal cord stimulation (a small implanted device that sends electrical pulses to the spinal cord to override pain signals) are options, though success rates vary.
Physical therapy plays a central role, with growing emphasis on techniques that target the brain changes underlying RSD. Graded Motor Imagery is a structured program that works in three stages. First, you practice identifying whether pictures show a left or right hand (or foot), which gently activates motor areas of the brain without triggering pain. Next, you imagine moving the affected limb. Finally, you progress to mirror therapy: watching the reflection of your healthy limb move while the affected one stays still, which tricks the brain into processing pain-free movement from the injured side. The goal is to gradually reverse the maladaptive brain rewiring that keeps the pain cycle going.
Long-Term Outlook
The course of RSD varies enormously. Roughly 60% to 70% of patients recover well by 12 months, while 25% to 29% achieve a moderate outcome and 9% to 14% are categorized as having poor outcomes. However, “recovery” doesn’t always mean symptom-free. Across multiple studies, only about 5% of patients report being completely free of all RSD symptoms at follow-up. Between 51% and 89% of patients continue to experience some degree of weakness, stiffness, or reduced range of motion at 12 months and beyond.
The functional impact can be significant. Patients typically retain a 20% to 25% reduction in range of motion and a 25% to 50% decrease in grip strength compared to their unaffected side, even after a year or more. About 60% to 70% of people who were working before their diagnosis return to work, but 27% to 35% of those who do return need modifications to their job roles. The remaining 30% to 40% do not return to work at all.
Early, aggressive treatment appears to make a meaningful difference. One small study that followed patients who received no treatment found that nearly all had resolved by 13 months, but larger studies consistently show that post-fracture RSD persists in 57% to 63% of patients at the one-year mark when left undertreated. The wide range of reported outcomes likely reflects differences in how early treatment begins, how severe the initial case is, and individual variation in nervous system response.