Floating Tophi in a Baker Cyst Secondary to Gout: Ultrasound Features and Differential Diagnosis.

We report the case of a 36-year-old man with a recent diagnosis of gout, who presents with a fullness behind his right knee that fluctuates in size with time. An ultrasound revealed a Baker cyst that contained both large and punctate internal hyperechoic foci. Cyst aspiration revealed negatively birefringent crystals, which were consistent with gout.