A Peculiar Case of Gas in Popliteal Cyst: Is there a Potential Association with Rheumatoid Arthritis?

Authors

  • Darren Wong Department of Diagnostic Radiology, Singapore General Hospital, Singapore
  • Cheong Wei Kiong Department of Diagnostic Radiology, Singapore General Hospital, Singapore

DOI:

https://doi.org/10.3941/jrcr.5805

Abstract

We report a rare case of atraumatic gas within a popliteal cyst in an elderly woman with seropositive rheumatoid arthritis. The patient presented with posterior knee swelling but no signs of infection or trauma. Imaging revealed soft tissue gas within the cyst, confirmed on radiographs and MRI. Aspiration yielded sterile, straw-coloured fluid without crystals or malignant cells. The patient remained well with conservative management. While only two similar cases have been reported, both also involved rheumatoid arthritis, suggesting a possible – but unproven – association. We discuss potential mechanisms, including altered synovial fluid gas dynamics in rheumatoid arthritis, and emphasize the importance of clinioradiological correlation to avoid unnecessary intervention.

Lateral radiographic view of the right knee showed multiple soft tissue gas projected over the posterior aspect of the proximal tibiafibula. (B) Follow-up radiograph performed 9 months later showed complete resolution of soft tissue gas.

Downloads

Published

2025-08-31

Issue

Vol. 19 No. 8 (2025)

Section

Musculoskeletal Radiology

License

Copyright (c) 2025 Journal of Radiology Case Reports

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

The publisher holds the copyright to the published articles and contents. However, the articles in this journal are open-access articles distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 License, which permits reproduction and distribution, provided the original work is properly cited. The publisher and author have the right to use the text, images and other multimedia contents from the submitted work for further usage in affiliated programs. Commercial use and derivative works are not permitted, unless explicitly allowed by the publisher.