Imaging of the symptomatic and swollen knee of a 17-year-old boy with JIA. (A) Axial US scanning lateral to the patella. The left image shows an anechoic recess composed of synovial thickening and effusion, measured (1) before compression. In the right image, compression of the recess has transposed the effusion and enabled measurement (1) of the hypertrophic synovium. (B) A 3D T1 gradient echo VIBE MRI image of the same joint showing the enhanced hypertrophic synovial tissue (syn), and the effusion (eff), following intravenous injection of Gadolinium contrast.