[Ultrasonography and computerized tomography in giant Baker's cyst].

The US study of the posterior compartment of the knee usually allows the clinical suspicion of popliteal cyst to be confirmed. Nevertheless, in case of giant Baker's cysts--which are, at any rate, less frequent--US diagnosis is more difficult. CT can help determine the benign nature of the lesion, and allow an accurate spatial evaluation. Moreover CT, when accurately performed, demonstrates the caudal or cranial cystic spread, together with its clear separation from adjacent muscular tissues. Direct coronal scans are more useful to obtain better spatial definition than reformatted images.