Lipoma arborescens of the knee: MR characteristics in 13 joints.
UNLABELLED: Lipoma arborescens (LA) is a rare, poorly understood intraarticular 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 anomalies. METHOD: The medical records and MR findings of 12 patients with proven LA in 13 knee joints were retrospectively reviewed with particular emphasis on the shape of the lesion, location, signal intensity, and past clinical history. RESULTS: We found three common morphological patterns of presentation: multiple villous lipomatous synovial proliferations (n = 6), isolated frond-like fat subsynovial mass (n = 2), and mixed pattern (n = 5). Multiple villous lipomatous synovial proliferations and mixed pattern were usually associated with a history of trauma and/or chronic inflammatory diseases. However, the least frequent isolated frond-like fat subsynovial mass appears to originate without antecedent. 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 study suggest that LA can present with a variety of morphological appearances on MR that may depend on the previous clinical history and duration of the disease.