Intraarticular steroid therapy in juvenile chronic arthritis (JCA) is performed because of high local efficacy with few side effects. Imaging is used for initial evaluation and for monitoring of treatment response. The aim of this study was to compare imaging findings in diseased hips and knees before and after therapy. A prospective study was performed on 10 patients (15 joints) scheduled for intraarticular therapy. Pretherapeutic assessment included clinical work-up, radiographs, ultrasound (US), and magnetic resonance imaging (MRI) of affected joints. Following therapy, clinical and sonographic examinations were performed at 1 week and 1 month. MRI was repeated at 1 month. MRI and US demonstrated pannus formation and effusion, but differentiation was less distinct on US. Popliteal cysts and lymph nodes were visible in both modalities. MRI additionally revealed articular cartilage loss and subchondral cysts, not shown by US. Epiphyseal overgrowth and osteopenia were best seen radiographically. At present MRI is the best tool to assess the inflammatory changes of the joints in JCA. Initial staging of the joints may be done with plain films and MRI. US is useful to assess effusion and pannus and may be used to monitor treatment response.