• Complex Regional Pain Syndrome (CRPS), also known as Reflex Sympathetic Dystrophy (RSD) or Causalgia, is a chronic neurological condition caused by a malfunction or “short circuit” in the nervous system.
• The condition causes the brain to receive constant pain signals that are often far out of proportion to the original injury.
• Symptoms may include burning pain, temperature or color changes, swelling, hypersensitivity, stiffness, and changes in skin or nail appearance.
• Early diagnosis and treatment—such as physical therapy, desensitization, pain‑modulating medications, and nerve‑targeted therapies—can improve outcomes and reduce long‑term disability.
Complex Regional Pain Syndrome (CRPS) is a poorly understood neurological phenomenon that is even more confusing because it goes by so many different names. It is also known as Reflex Sympathetic Dystrophy (RSD), Sudecks Atrophy and causalgia.
The condition is basically a short circuit of the nervous system where nerves misfire thus sending constant pain signals to the brain even though there is no real or limited pain going on. In other words, it is a completely abnormal response by the nervous system to external stimuli.
CRPS can occur anywhere on the body but is fairly common in the foot and leg. Pain is out of proportion to an injury; the pain may be severe, constant or burning. There may be a hypersensitivity to external stimuli like heat or cold.
There are three stages in this condition, although most people do not necessarily have to go through all of the stages.
Timing: Starts immediately or several weeks after injury (including foot or leg surgery).
The skin becomes dry and red, transitioning to cool and moist within weeks. The foot and lower leg typically swell, joint movement becomes limited, and constant pain is present—often only alleviated by sleep or medication. In some cases, osteoporosis may begin here.
The skin becomes increasingly moist, tight, and shiny. Nails may become brittle and cracked. Patients often develop a guarded gait because the joints of the foot and ankle feel "locked."
This stage is characterized by irreversible structural changes, including soft tissue atrophy (wasting) and decalcification of the bone. Pain often worsens, becomes intractable, and may spread beyond the original site. The skin typically appears cool and dry.
Look at the picture of the feet below. Note the increased redness in the right foot. This patient had undergone surgery on the right foot, had been in a cast, and CRPS developed afterwards.
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The following x-ray reveals the severe osteoporosis
that can occur. Look how demineralized the middle of the foot appears.
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There are two types of CRPS, Type I and Type II. Type I is also referred to RSD and these involve cases in which the nerve injury cannot immediately be identified. Type II also referred to as Causalgia involves cases where there has been a major trauma to a distinct nerve.
There really is no laboratory test to diagnose Complex Regional Pain Syndrome. It is diagnosed on clinical grounds particularly to a nerve or soft tissue injury which does not respond in a normal healing path.
A thorough medical history and physical examination are necessary. It should be noted that in this instance surgery can be considered as an injury. CRPS has been seen quite frequently following elective foot surgery where the foot and lower leg required immobilization for a period of time due to the type of surgery performed.
It is estimated that people go to as many as five doctors before the proper diagnosis is made. The problem with this is that valuable time is wasted in beginning treatment. The earlier treatment is instituted , the better the prognosis.
There are basically three types of specialists that are the most likely to make a proper diagnosis and they should be consulted for treatment.
Even going to one of these specialists does not guarantee proper diagnosis and treatment. You should ask your physician if he or she is experienced in treating this condition.
Treatment, of course, is based on the severity of the presenting symptoms. Treatment options includes:
The points to take away from this discussion of Complex Regional Pain Syndrome is that it is a diagnosis that is often overlooked and because of the delay in treatment, or even under treatment, permanent pain and disability may arise. Additionally there are only a few types of specialists that are properly experienced to adequately treat this condition.
REFERENCES
My husband had surgery 3 weeks ago on his ankle to remove two lesions from a previous injury. He also has an incision on the lateral portion of his foot from where they thought they would do a tendon and ligament repair, but after getting inside they felt it wasn’t necessary.
Surgery went great. The splint came off after 2 weeks and he is now non‑weight‑bearing with a boot, allowed to flex and extend the foot, which he does many times a day. Capillary refill is great, bruising is going down, and the incisions look great.
The only problem is that his foot remains cold as ice even with thick socks on. The skin is maybe a little pale, but not dramatically different from the other foot. Should we be concerned? If he has decreased circulation due to lack of movement, could this greatly affect healing?
Hi Tina,
Two possible conditions come to mind after reading your narrative. Keep in mind I am not making a diagnosis, as that is impossible from the other side of the internet.
The first possibility is Complex Regional Pain Syndrome (CRPS). This happens in individuals who have had foot surgery and generally end up in a boot or cast. It is essentially a short‑circuiting of the nerve transmission from the foot to the brain and the brain to the foot. You can read about it on my site. It can be difficult to diagnose, and the further along it goes, the more difficult it is to treat. If not diagnosed and treated, it can have debilitating effects.
The second possibility is an arterial embolism or a blood clot in one of the arteries that goes down the leg. I know nothing about your husband’s medical history or even his age, so I have no idea if he is at greater risk for this problem. If an artery is being blocked, then everything below the blockage will be colder and paler.
When one foot is noticeably colder and paler than the other, that is a sign of diminished circulation coming into the colder foot. That is not good and needs to be addressed immediately, regardless of the source.
I would call his surgeon immediately, and if for some reason you cannot get in touch with them, then I would suggest taking him to your local Emergency Room and having the foot checked out.
Marc Mitnick DPM
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DISCLAIMER: The purpose of this site is purely informational in nature. It is not intended to diagnose, treat or cure any medical condition. This information is not a substitute for advice from a medical professional. Please consult your healthcare provider for accurate diagnosis and treatment. The information presented here may be subject to errors and omissions.
SITE LAST UPDATED: MAY 2026


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