CT findings of suprapatellar synovial cysts

The computed tomographic (CT) findings of two suprapatellar (SP) synovial cysts are presented, and the correlated anatomicopathologic changes are discussed. The cysts show characteristically semilunar shapes and anteromedial locations in the SP regions with superolateral extension. The cyst walls vary in thickness, and the cyst contents also vary from a transudate to a thick mucoid fluid, which may show a high attenuation value on CT. Differential diagnoses include liposarcoma, hematoma, xanthoma, fibrosarcoma, or other soft tissue tumors.