Reflex sympathetic dystrophy
aka Complex Region Pain Syndrome, Transient Osteoporosis
Poorly understood entity of non-anatomic, disproportionate pain, with vasomotor disturbances and trophic changes. No specific pathologic, histologic or biochemical markers exist.
Image is of a health 31 y.o. male who presents with ankle pain after a knee injury two months prior. Right foot demonstrates osteopenia while the contralateral foot is normal.
Plain radiographs show only local osteopenia. Three phase nuclear medicine bone scan very sensitive.