Nuclear Medicine and Molecular Imaging

, Volume 53, Issue 5, pp 349–355 | Cite as

Calf “Arch Sign” Seen on a Tc-99m-MDP Bone Scan Is Indicative of Synovial Fluid Leak in Ruptured Baker’s Cysts: Case Reports and Analysis of Literature

  • Haim Golan
  • Evgeniya Fridburg
Case Report


The authors present two cases in which the ruptured popliteal (Baker’s) cysts remained undetected and were diagnosed only during an isotope investigation. The aim was to describe a specific imaging sign, the “arch sign”, that is indicative of ruptured Baker’s cysts. In both cases, the whole-body imaging was performed 2 hours after injection of 706.7 MBq of Tc-99m-MDP. Single-photon emission computed tomography (SPECT) imaging was performed to localize an accumulation of the radiopharmaceutical. An analysis of literature was performed to connect these cases with previously reported data and to detect the pathognomonic radio image sign of ruptured popliteal cysts. The arch-shaped distribution of the radiopharmaceutical below the knee joints was seen already on the whole-body bone scan image in both cases. An anterior view of SPECT MIP images showed the arched accumulation of the Tc-99m-MDP bone tracer along the postero-medial aspect of the right calf secondary to synovial fluid leak from a ruptured Baker’s cyst. The similar arthroscintigrams were published since 1971 without recognizing this sign as pathognomonic. Tc-99m-MDP bone scanning is sensitive for a Baker’s cyst with synovial effusion, and distribution of a radiopharmaceutical in the medial posterior calf in a shape of an arch, the arch sign, may serve as an indicator of a ruptured popliteal cyst.


Popliteal cysts Ruptured Baker’s cysts Tc-99m-MDP SPECT 



The authors thank Michael Shterenshis for editing assistance.

Compliance with Ethical Standards

Conflict of Interest

Haim Golan and Evgeniya Fridburg declare that they have no conflict of interest.

Ethical Approval

The research did not involve human participants and/or animals because only images and previously obtained data from the charts were analyzed. No personal details of patients appear in the article as in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed Consent

The institutional review board of our institute approved this retrospective study, and the requirement to obtain informed consent was waived.


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Copyright information

© Korean Society of Nuclear Medicine 2019

Authors and Affiliations

  • Haim Golan
    • 1
    • 2
  • Evgeniya Fridburg
    • 1
  1. 1.Departmentof Nuclear Medicine, Assaf Harofeh Medical Center Affiliated to Sackler Faculty of MedicineTel Aviv UniversityZerifinIsrael
  2. 2.ZerifinIsrael

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