Imaging of the symptomatic ankle region of an 11-year-old girl with JIA. (A) Sagittal US scanning of the anterior talo-crural joint showing synovial hypertrophy (syn) to the left and hyperemia (hyp) on color Doppler to the right. (B) T1-weighted sagittal MRI images before (left) and after (middle) contrast injection. The left image reveals a small bony erosion at the neck of the talus (arrowhead). The erosion is surrounded by bone marrow edema (arrowhead, middle image). In the same image synovial hypertrophy with contrast enhancement (syn) and effusion (eff) are visualized in the anterior and posterior recesses of the talo-crural (tc) and posterior subtalar (pst) joints. On the STIR image to the right, high signal intensity depicts the location of synovitis (syn + eff) and the bone marrow edema surrounding the erosion (arrowhead, right image).