Baker's cyst simulating deep vein thrombosis.

Phlebography is frequently requested to confirm or exclude deep venous thrombosis in patients presenting with a painful, swollen calf or leg. We have noted a small proportion of those with negative phlebograms to have compression or lateral deviation of the popliteal vein. These patients were submitted to contrast arthrography. Eighty per cent of this selected group were found to have dissecting or ruptured Baker's cysts; almost a third of these were dissections upwards into the thigh. A positive diagnosis in these patients is important as management differs from deep vein thrombosis. The optimum diagnostic strategy in patients with a swollen, painful leg is firstly to perform ultrasound of the femoral vein and popliteal fossa to exclude obvious thrombus or ruptured Baker's cyst. If this examination is negative, or a Baker's cyst is shown with no evidence of rupture, phlebography should be performed to exclude calf vein thrombosis. If this examination is negative, but a Baker's cyst is present, or deviation or compression of the popliteal vein is detected, contrast arthrography is suggested to look for rupture of the cyst.