CRPS is a debilitating chronic pain condition primarily affecting the distal limbs. It is characterized by a constellation of signs and symptoms, including hyperalgesia, allodynia, skin trophic changes, edema, limited range of motion, vasomotor instability, and disproportionate pain, often accompanied by patchy bone demineralization.1, 2, 3, 4 The pathophysiology of CRPS remains poorly understood; however, various triggering factors such as prior trauma, fractures, surgical interventions, or soft tissue injuries have been frequently implicated in its onset.1,2,5,6

The reported incidence ranges from 0.31% to 0.69%, with higher prevalence in females. CRPS can be classified into Type I (without peripheral nerve injury), Type II (with peripheral nerve injury), CRPS-NOS (not otherwise specified), and CRPS-F (focal, proposed in newer taxonomies).7, 8, 9, 10 Additionally, it can be clinically categorized as hot vs. cold or acute vs. chronic.11, 12, 13 While CRPS can manifest at any age, it is relatively rare in children and adolescents.10

Several mechanisms have been proposed to explain the pathophysiology of CRPS. Alterations in both the peripheral and central nervous systems have been described, including classic and neurogenic inflammation, maladaptive changes in pain perception, central sensitization, and sympathetic overactivity.14, 15, 16, 17, 18, 19 In addition, increased osteoclast activity may contribute to the focal bone changes frequently observed in affected limbs.20, 21

For diagnosis, the Budapest criteria currently serve as the international standard.22 More recently, the Valencia consensus has proposed an adaptation of the IASP criteria, aiming to refine the classification and clinical applicability of CRPS.23 Despite these advances, diagnosis remains challenging, and complementary imaging techniques have been investigated. Triple-phase bone scintigraphy (TPBS), plain radiography, and autonomic testing offer limited diagnostic accuracy, while MRI may provide supportive findings but is not definitive.24, 25, 26

Within this context, dual-energy X-ray absorptiometry (DXA) has emerged as a potentially useful tool to assess CRPS-related bone involvement. Prior studies have reported reductions of approximately 30% in BMD in the affected limb.27 Therapeutic approaches for CRPS include pharmacological strategies—such as bisphosphonates, calcitonin, corticosteroids, vitamin D supplementation, and neuropathic pain medications—and non-pharmacological interventions including physical therapy, desensitization, and neuromodulation.2,28

Our research group has previously established baseline BMD values in hands and feet of healthy individuals, using total and region-specific validated ROIs.29 Building upon this knowledge and the limited evidence available in CRPS, the objective of the present study was to investigate BMD differences between affected and unaffected feet in CRPS patients. We hypothesized that BMD would be significantly lower in the affected foot compared with the contralateral foot.