1. Figure 4a: Axial CEcontrast material enhanced knee MR images in a 22-year-old man with a history of lipoma arborescens excision in the left knee. (a) FSfat suppressed PDproton density-weighted image shows a large joint effusion with prominent synovial proliferation in the lateral part of the suprapatellar recess (arrows). (b) FSfat suppressed T1-weighted image obtained after intravenous gadolinium-based contrast material injection demonstrates the enhancing synovium with excellent tissue contrast (arrow), while the nonenhancing synovial tissue regarded as chronic synovial inflammation with fibrosis in the lateral part of the suprapatellar recess was not seen. (c) FLAIRfluid-attenuated inversion recovery FSfat suppressed image also demonstrates the synovium, showing both the synovium (black arrow) and chronic synovial hypertrophy (white arrows).