MRI Findings of Synovial Lipoma Arborescens of the Hip: A Case Report

consisting of villous lipomatous proliferation of the synovium that tends to occur in the knee joint, especially in the suprapatellar pouch (1). The lesion has been observed in other locations, including the glenohumeral joint, subdeltoid bursa, hip, and elbow (2). It may be similar to other proliferations of the synovial membrane, but the characteristic feature is the macroscopic hypertrophic lipomatous synovial tissue. The term “arborescens” describes the characteristic tree-like morphology of this lipomatous villous synovial proliferation, which resembles a frond-like synovial mass (3). Involvement of the hip joint is rarely encountered. To our knowledge, only a few cases were reported. Wolf RS et al. (4) and Noel ER et al. (5) reported hip joint involvement of LA in previous orthopedic and rheumatologic literatures. However, the radiologic literature indicating solitary involvement of the hip joint has not been reported. We report a case of MR imaging on a lipoma arborescens of the hip joint, which was pathologically confirmed. The MRI findings were found to help the early diagnosis of this disorder.