Pain and swelling of the lower extremity following total knee arthroplasty are not infrequent. The most frequent conditions responsible for these symptoms include thrombophlebitis, prosthetic loosening, infection, and fracture of either the prosthesis or the bones. In addition to these conditions, a dissecting or ruptured popliteal cyst should be considered in the differential diagnosis of acute calf pain and swelling following total knee arthroplasty. Two patients with symptoms of phlebothrombosis were evaluated retrospectively two to three years following total knee arthroplasty. In both patients the popliteal cysts dissected proximally into the thigh. A dissecting popliteal cyst is diagnosed by arthrography. The usual arthrographic films evaluated for a Baker's or popliteal cyst are anteroposterior and lateral views of the calf. These films are inadequate in patients who have undergone total knee arthroplasty; the dissecting cysts observed in the patients of the present report dissected proximally above the knee and were diagnosed on anteroposterior and lateral views of the distal femur. The more common symptoms noted after total knee arthroplasty should not be excluded due to the presence of a dissecting or ruptured cyst, as one of the patients of the present report also had a superimposed infection. Clinical considerations of a dissecting popliteal cyst are emphasized so that arthrography can be performed early in the course of the symptoms and proper treatment initiated.