Lipoma arborescens: high-resolution ultrasonographic findings.

Three patients with lipoma arborescens of the knee joint were evaluated with high resolution ultrasonography. All patients demonstrated a hyperechoic, frondlike mass in the suprapatellar bursa with a large associated effusion. All had popliteal cyst formation without involvement by the mass. Dynamic compression and manipulation of the suprapatellar effusion demonstrated pliable and flexible nature of mass with bending and waving of the frondlike mass in real time. Comparison with MR imaging demonstrated similar extent, location, and morphology of the mass. The characteristic features of this lesion as well as its distribution in the knee joint can be demonstrated readily by sonography.