title: Pyogenic arthritis presenting as a ruptured popliteal cyst.
mesh_terms: D001170:Arthritis, Infectious / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D006801:Humans; D007717:Knee / Q000000981:diagnostic imaging; D011859:Radiography; D012422:Rupture, Spontaneous; D013581:Synovial Cyst / Q000000981:diagnostic imaging*