A 14-year-old boy presents 6 months after spraining his right ankle. Radiographs obtained at the time of injury are shown in Figure A. He returns to clinic with persistent right ankle pain. The patient denies fevers, and has an ESR of 35 mm/h (nl 0-20). CRP and WBC are normal. Current radiographs and MRI images are shown in Figures B, C, and D. What is the next most appropriate step in management?