Osteochondritis dissecans of talus in college football player. A, Coronal T1-weighted image shows osteochondral fragment in medial talar dome. Loss of fat signal suggests sclerosis or fibrosis (arrow). B, Coronal fat-suppressed, T2-weighted image demonstrates fluid signal between lesion and host bone (arrowheads), indicating unstable fragment. C, Coronal fat-suppressed, spoiled gradient-echo technique reveals abnormal decreased signal (arrow) in overlying articular cartilage, indicating defect confirmed by arthroscopy.