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Remote Fellowship – Foot & Ankle Fundamentals – 11/2/2020

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Complex Regional Pain Syndrome

Case Discussion

Complex Regional Pain Syndrome (CRPS) is a chronic pain condition that typically affects an extremity after an inciting injury or surgery.  The inciting injury may be minor. Symptoms are related to autonomic dysregulation/hypersensitivity and include edema, changes to skin blood flow, abnormal motor activity and allodynia and are often out of proportion to the initial event. There are two types of CRPS:

– Type 1 (formerly known as Reflex Sympathetic Dystrophy) is characterized by the absence of an underlying single nerve lesion

– Type 2(formerly known as Causalgia) is characterized by the presence of an underlying nerve lesion

In both types of CRPS there are three different stages of the disease:

MRI findings of CRPS include: patchy bone marrow edema (specifically, peripheral/subcortical “window-framing pattern” of osteoedema), soft tissue edema and enhancement, skin thickening, joint effusions, synovial hypertrophy, and muscle atrophy in later stages. Unlike the patchy random bone marrow edema pattern routinely seen in juveniles due to skeletal hyperemia and increased bone turnover, CRPS is subcortical and peripheral, whereas the former is more central in the medullary bony space.

An early diagnosis is imperative, given that severe untreated autonomic dysregulation may lead to autoamputation of the affected extremity. 

Treatment options include physiotherapy/movement and sympathectomy (chemical sympathectomy via lumbar nerve block).

Key Images

Complex regional pain syndrome (formerly known as RSD) in a 14-year-old girl with a history of fibular fracture 4-5 months prior, now complaining of continued right ankle pain, swelling, and locking symptoms

A. Sagittal STIR image of the right ankle shows patchy, peripheral “window frame” type osteoedema throughout the midfoot and hindfoot (red arrows).


  1. Nishida Y, Saito Y, Yokota T, Kanda T, Mizusawa H. Skeletal muscle MRI in complex regional pain syndrome. Inter Med 2009; 48:209-212
  2. Harden RN, Oaklander AL, Burton AW, et al. Complex regional pain syndrome: Practical diagnostic and treatment guidelines. Pain Medicine 2013; 14(2) 180-229