LIPOMA ARBORESCENS OF THE KNEE - MR CHARACTERISTICS IN 13 JOINTS

Purpose: Lipoma arborescens (LA) is a rare, poorly understood intraart icular lesion, with few cases reported in the imaging literature. Our purpose was to describe on MR the different morphologic appearances of LA of the knee and to investigate the incidence of associated anomali es. Method: The medical records and MR findings of 12 patients with pr oven LA in 13 knee joints were retrospectively reviewed with particula r emphasis on the shape of the lesion, location, signal intensity, and past clinical history. Results: We found three common morphological p atterns of presentation: multiple villous lipomatous synovial prolifer ations (n = 6), isolated frond-like fat subsynovial mass (n = 2), and mixed pattern (n = 5). Multiple villous lipomatous synovial proliferat ions and mixed pattern were usually associated with a history of traum a and/or chronic inflammatory diseases. However, the least frequent is olated frond-like fat subsynovial mass appears to originate without an tecedent. The durations of symptoms were 1-7 months (multiple villous lipomatous synovial proliferations), 1-20 years (mixed pattern), and 6 -7 years (isolated frond-like subsynovial fat mass). Conclusion: Our s tudy suggests that LA can present with a variety of morphological appe arances on MR that may depend on the previous clinical history and dur ation of the disease.