Complex regional pain syndrome (CRPS) is one of the most painful conditions in medicine. On the McGill Pain Scale, a widely used research tool that rates pain intensity out of 50, CRPS scores approximately 42 out of 50, higher than childbirth, amputation, and most other chronic pain conditions. Type 2 CRPS, which involves confirmed nerve damage, has been reported to score as high as 47 out of 50.
What the Pain Actually Feels Like
People with CRPS most commonly describe a deep, constant burning sensation in the affected limb, as if it’s being held over a flame. Others feel a persistent squeezing pressure or a “pins and needles” sensation that never lets up. This baseline pain is relentless, present even at rest, and it tends to intensify with movement or changes in temperature.
What makes CRPS uniquely agonizing is how the nervous system amplifies everyday sensations. A condition called allodynia causes things that shouldn’t hurt at all, like a bedsheet brushing against your skin, the weight of a sock, or a light breeze, to trigger severe pain. A related phenomenon called hyperalgesia turns minor discomfort, like a small pinprick, into prolonged, intense pain far out of proportion to the stimulus. Together, these mean that a person with CRPS can be in excruciating pain from simply existing in the world. Getting dressed, being touched by another person, or resting a limb on a surface can all become ordeals.
Why the Pain Is So Extreme
CRPS pain isn’t just about the original injury. In most cases, the nervous system itself malfunctions and becomes a source of pain. After an injury (sometimes as minor as a sprain or a surgery), the spinal cord’s pain-processing neurons become hyperexcitable. They start amplifying pain signals and interpreting harmless input as dangerous. This process, called central sensitization, is essentially the volume knob on pain getting turned up and stuck there.
The brain physically reorganizes in response. The area of the brain’s sensory map that corresponds to the affected limb actually shrinks, and the degree of this reorganization correlates with how intense the pain is. So CRPS isn’t “just” pain from an injury that won’t heal. It’s the nervous system rewriting its own wiring in ways that generate and sustain pain independently.
The body’s fight-or-flight system also gets involved. Pain-sensing nerve fibers in the affected area develop extra receptors for stress hormones, creating a feedback loop: stress and sympathetic nervous system activity directly increase pain, which causes more stress, which increases pain further. This same system drives the visible signs of CRPS, including skin color changes, temperature swings, and swelling in the affected limb.
Type 1 vs. Type 2
CRPS comes in two forms. Type 1, previously called reflex sympathetic dystrophy, develops without a confirmed nerve injury. It can follow a fracture, surgery, or even a seemingly minor sprain. Type 2, historically called causalgia, occurs when there is a documented nerve injury. Both types produce the same spectrum of symptoms. Type 2 may score slightly higher on pain scales, but both are capable of producing extreme, life-altering pain.
Beyond Pain: The Full Symptom Picture
Pain dominates CRPS, but the condition affects far more than sensation. To be diagnosed using the current clinical standard (known as the Budapest Criteria), a person must show symptoms across four distinct categories: sensory changes like allodynia, blood flow changes like skin color shifts or temperature differences between limbs, swelling or sweating abnormalities, and movement problems like weakness, tremor, or reduced range of motion. Changes in hair growth, nail texture, and skin quality also develop over time.
A hallmark of CRPS diagnosis is that the pain is “disproportionate to any inciting event.” In practical terms, this means someone might break a wrist, have it heal normally on imaging, and still be left with pain and dysfunction that far exceeds anything the original fracture should have caused. That disproportion is a core feature of the disease, not a sign that the pain isn’t real.
The Psychological Weight
Living with pain this severe takes a staggering psychological toll. People with CRPS frequently experience depression, anxiety, anger, frustration, and hopelessness. The condition restricts nearly every area of daily life, from work to sleep to relationships. Epidemiological data shows that 49.3% of people with CRPS have considered suicide, and the actual attempt rate is 15.1%, rates significantly higher than both the general population and people with other chronic pain conditions. These numbers reflect the reality that CRPS pain is not something people simply adjust to over time.
How Often CRPS Resolves
A prospective study tracking patients over their first year found that most signs and symptoms improve somewhat, with the greatest gains happening in the first six months. After that, progress tends to plateau. At the one-year mark, the picture was far less hopeful than many people expect: nearly two-thirds of patients still met clinical criteria for CRPS, one-quarter met the stricter research diagnostic criteria, and only 5.4% were completely symptom-free. CRPS can go into remission, but complete resolution within the first year is uncommon.
What Pain Management Looks Like
No single treatment reliably eliminates CRPS pain, but several approaches can reduce it meaningfully for some people. Ketamine infusions, which work by interrupting the central sensitization process, produce meaningful pain relief lasting one to three months in roughly 20% to 65% of patients, depending on the dose and protocol. Across studies, about half of CRPS patients achieve some form of long-term response. In one intensive protocol, approximately 50% of patients remained completely pain-free for 5 to 11 years, though this involved much higher doses under heavy sedation and is not widely available.
Spinal cord stimulation, a surgically implanted device that delivers electrical pulses to interrupt pain signals, has shown effectiveness for pain reduction in randomized trials. However, one study found that its advantage over physical therapy alone disappeared by the five-year mark. A newer variation called dorsal root ganglion stimulation showed a higher proportion of patients reporting relief at 12 months compared to traditional spinal cord stimulation.
Physical and occupational therapy remain central to treatment, not because they reduce pain directly, but because they help preserve function and prevent the affected limb from deteriorating further. For many people with CRPS, the goal of treatment shifts from eliminating pain to managing it well enough to maintain some quality of life, a reality that underscores just how severe this condition is.