We describe two patients who had knee pain and were found to have the unusual combination of a Baker's cyst and true thrombophlebitis. Since Baker's cysts can dissect along the gastrocnemius, they can cause leg pain and simulate thrombophlebitis, but they do not require anticoagulation therapy. Most of the literature implies that the two syndromes are mutually exclusive; however, our cases lend support to the fact that a dissecting popliteal cyst does not rule out the possibility of thrombophlebitis. Venography should be performed if there is any doubt as to the diagnosis.
(Arch Intern Med 139:40-42, 1979)