Baker cyst as seen on a PET/CT scan.

We present the case of a 48-year-old woman who had been diagnosed with multiple myeloma a year ago. She had persistent pain in her right knee that she tended to ignore. As part of her follow-up she underwent a PET/CT scan that did not show any metastatic lesions. However, a focal rounded area of FDG uptake behind her right knee showed a fluid density on the CT scan. A presumptive diagnosis of Baker cyst was suggested. Review of her previous MRI report performed at another hospital corroborated this finding.