Putative Physiopathological Explanation for the "Sock Sign" in Bone Scans

Clin Nucl Med. 2016 Sep;41(9):e420-1. doi: 10.1097/RLU.0000000000001255.


Four patients were referred to our department to undergo a bone scan for suspected reflex sympathetic dystrophy in the upper limbs. After TC-HMDP injection in the foot, they developed a "sock sign," defined by highly increased uptake in the injected lower limb. The sock sign has been previously described in only 1 case in the literature and attributed to intra-arterial injection. Our images suggest that the sock sign might instead be the consequence of tracer extravasation at the injection site.

Publication types

  • Case Reports

MeSH terms

  • Bone and Bones / diagnostic imaging*
  • Extravasation of Diagnostic and Therapeutic Materials / diagnostic imaging*
  • Foot / diagnostic imaging*
  • Humans
  • Injections, Intra-Arterial
  • Injections, Intravenous
  • Lower Extremity
  • Middle Aged
  • Radiopharmaceuticals
  • Reflex Sympathetic Dystrophy / diagnostic imaging*
  • Technetium Tc 99m Medronate / analogs & derivatives


  • Radiopharmaceuticals
  • technetium Tc 99m hydroxymethylene diphosphonate
  • Technetium Tc 99m Medronate