Knee Pain in a 17-year-old Girl

A 17-year-old girl presented with a 1-month history of right knee pain after repeated strenuous martial art training. She had no medical history. Point tenderness during palpation of the posteromedial aspect of the knee was noted. The rest of the physical examination was within normal limits and laboratory data were entirely normal. Radiography (Fig. 1), ultrasound (Fig. 2), MRI (Fig. 3), and CT (Fig. 4) of the right knee were performed. Based on the history, physical examination, laboratory studies, and imaging studies, what is the differential diagnosis?