UNDERSTANDING CRPS
What is CRPS?
Complex Regional Pain Syndrome is a persistent pain condition that usually affects an arm or leg, often after an injury or surgery. The pain is typically greater or longer-lasting than expected and can be accompanied by changes in sensation, temperature, color, swelling, sweating, movement and the tissues of the affected area.
CRPS AT A GLANCE
A condition that involves more than pain.
01
Usually regional
It most often begins in one limb, but symptoms can extend beyond the original injury site.
02
Often follows an injury
Fractures, sprains, surgery and other forms of trauma can precede CRPS.
03
Multiple systems are involved
Sensory, vascular, sweating, swelling, movement and tissue changes can occur together.
04
Diagnosis is clinical
There is no single blood test, scan or procedure that confirms CRPS by itself.
IN THIS GUIDE
THE CONDITION
Why CRPS is called “complex”
CRPS is not defined by pain alone. It can involve abnormal pain processing, inflammation, blood-flow and temperature regulation, swelling, sweating, movement and changes in skin, hair or nails.
THE CORE FEATURE
Continuing pain that is disproportionate to the original event
The pain can be burning, stabbing, throbbing or electric in character. A light touch, clothing, pressure or temperature change may become unusually painful. For diagnosis, clinicians look at the pain together with a broader pattern of symptoms and physical signs.
Important: The original injury does not have to be severe. The intensity of CRPS is not determined simply by how serious the initial injury appeared.
01
Sensory
Increased sensitivity, hyperalgesia and pain from normally non-painful touch or pressure.
02
Vasomotor
Changes or asymmetry in skin temperature and color between the affected and unaffected side.
03
Swelling & sweating
Edema and changes or asymmetry in sweating can be part of the CRPS pattern.
04
Motor & trophic
Reduced movement, weakness, tremor or dystonia, together with possible skin, hair or nail changes.
SIGNS & SYMPTOMS
CRPS can look different from one person to another.
Symptoms may fluctuate over time and not every person experiences every feature. What matters clinically is the overall pattern, what the patient reports and what can be observed during examination.
01
Pain & sensitivity
- Persistent regional pain
- Burning, shooting, stabbing or throbbing sensations
- Allodynia: pain from normally non-painful touch
- Hyperalgesia: exaggerated response to painful stimuli
02
Temperature & color
- The affected area may feel warmer or colder
- Red, pale, blue or mottled skin can occur
- Appearance may change during the day
- Differences can be obvious compared with the opposite limb
03
Swelling & sweating
- Swelling of the affected region
- Changes in sweating
- Asymmetrical sweating between limbs
- Symptoms may increase or decrease over time
04
Movement & strength
- Reduced range of motion
- Weakness or difficulty using the limb
- Tremor or muscle spasm in some patients
- Dystonia can occur in some cases
05
Skin, hair & nails
- Changes in skin texture
- Altered hair growth
- Changes in nail growth or appearance
- Other trophic changes may develop
06
Daily life
- Sleep can be disrupted by pain
- Walking, dressing or using the hand can become difficult
- Work and independence may be affected
- Persistent pain can place a major emotional burden
WHEN TO SEEK AN EVALUATION
Persistent pain that is much greater than expected deserves attention.
If pain continues after an injury or procedure and is accompanied by swelling, unusual sensitivity, temperature or color changes, or increasing difficulty moving the limb, a medical evaluation should not be unnecessarily delayed.
CRPS-I & CRPS-II
Two types. Similar symptoms. One important distinction.
The distinction between CRPS type I and type II is based on whether a specific nerve injury has been identified. The clinical symptoms themselves can be very similar.
TYPE I
CRPS-I
Previously called Reflex Sympathetic Dystrophy (RSD)
CRPS-I occurs without an identified injury to a specific nerve. It may follow a fracture, sprain, surgery, immobilization or another injury.
TYPE II
CRPS-II
Previously called Causalgia
CRPS-II occurs after a known injury to a specific nerve. The presence of that nerve injury is what separates type II from type I.
Having CRPS-I does not mean that the pain is less real or less severe. The type describes the relationship to an identifiable nerve injury, not the intensity of the condition.
HOW CRPS CAN CHANGE
“Warm” and “cold” CRPS are better understood as clinical patterns — not a fixed timetable.
CRPS often changes in appearance over time, but research does not support a universal sequence of rigid stages that every patient follows. Studies instead describe recognizable warm and cold phenotypes.
A person can also show a mixture of features, and the pattern seen at one visit may not fully describe the course of the condition.
WARM PATTERN
Warm · red · swollen
A warmer limb, redness, swelling and increased sweating are commonly associated with a warm CRPS presentation.
COLD PATTERN
Cool · pale or bluish
Some patients have a colder limb with pale or bluish color and a different vascular pattern.
PLAIN-LANGUAGE TAKEAWAY
Do not assume that you can determine how long someone has had CRPS—or what treatment they need—simply from whether the limb looks “warm” or “cold”.
DIAGNOSIS
There is no single test for CRPS.
Diagnosis is based on the clinical history, symptoms, physical signs and the exclusion of another condition that would better explain the presentation. Blood tests, imaging or nerve studies may be used when clinicians need to investigate alternative causes.
IASP ACCEPTED FRAMEWORK
The Budapest clinical criteria
01
Continuing pain
Pain that is disproportionate to the original event.
02
Patient-reported symptoms
At least one symptom in three of the four domains: sensory, vasomotor, swelling/sweating and motor/trophic.
03
Observed clinical signs
At least one sign is present during examination in two or more of the four domains.
04
No better explanation
No other diagnosis better explains the signs and symptoms.
01
History matters
A clinician will usually ask how the problem started, how symptoms evolved, what makes them change and how the affected region compares with the opposite side.
02
Examination matters
Temperature, color, swelling, sweating, sensitivity, movement and trophic changes can all form part of the clinical examination.
03
Tests can rule out alternatives
Imaging, blood tests or nerve studies may be useful when another diagnosis needs to be excluded, but none of them confirms CRPS on its own.
Important: The Budapest Criteria are clinical diagnostic criteria, not a self-test. Similar symptoms can occur in other conditions, which is why an appropriate clinical assessment matters.
WHY DOES CRPS HAPPEN?
There is no single simple mechanism.
CRPS frequently begins after an injury or surgery, but researchers still do not have one explanation that accounts for every case.
Current models involve interactions between the peripheral and central nervous systems, inflammation and immune signaling, blood-flow and autonomic regulation, sensory processing and changes related to movement and limb use.
This complexity helps explain why the condition can look different between patients and why assessment often needs more than one clinical discipline.
WHAT TO DO NEXT
If CRPS is suspected, turn uncertainty into useful information.
A clear symptom history can make a clinical appointment more productive. You do not need to diagnose yourself—you need to help the clinician see the pattern.
01
Build a timeline
Write down the original injury or procedure, when the pain changed and when other symptoms appeared.
02
Document changes
Temperature, color and swelling can fluctuate. Notes or dated photographs can help describe what you experience.
03
List previous treatments
Bring medication names, procedures, rehabilitation history, imaging and relevant medical reports.
04
Ask what comes next
Discuss diagnosis, rehabilitation, symptom management and treatment options appropriate to your situation.
CONTINUE EXPLORING
Understanding CRPS is the first step.
From here you can explore the treatment information and practical support areas of CRPS Support.
01
What is neridronate?
Understand the medication, the scientific evidence and its status in Italy.
02
Treatment in Italy
Compare the treatment settings currently listed by CRPS Support.
03
Patient support
Contact Carla Crowe for practical information and patient orientation.
QUICK ANSWERS
Common questions about CRPS
Use these answers as an introduction, then explore the detailed sections above.
Yes. CRPS can follow injuries of different severities. The intensity of the syndrome is not simply proportional to how serious the original injury seemed.
CRPS usually begins in one region or limb, but symptoms can sometimes extend beyond the original area or affect additional regions.
No. There is no single imaging study or laboratory test that confirms CRPS. Diagnosis is clinical; tests are often used to look for alternative explanations.
No fixed sequence occurs in every patient. Warm and cold presentations are useful clinical patterns, but individual courses are variable and mixed features can occur.
Outcomes vary. Some people improve substantially, while others have persistent or fluctuating symptoms. Prompt assessment and an individualized management plan are important when CRPS is suspected.
SOURCES & FURTHER READING
Built from recognized clinical and scientific sources.
This page is written for patients, so technical concepts have been translated into plain language. Use the original sources below for the clinical detail.
NIH · NINDS
Complex Regional Pain Syndrome
Overview, CRPS-I vs CRPS-II, symptoms, causes and current patient information.
IASP
Complex Regional Pain Syndrome resources
Includes the IASP-accepted Budapest diagnostic criteria and CRPS research resources.
PAIN MEDICINE · 2022
CRPS Practical Diagnostic and Treatment Guidelines, 5th Edition
Expert diagnostic and treatment guidance from a multidisciplinary author group.
NHS
CRPS diagnosis
Patient-oriented explanation of clinical assessment and tests used to exclude other causes.
Scientific content reviewed for this page: August 2026.
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