A and B, Large osteochondritis dissecans defect on lateral femoral condyle seen on radiograph and MR image. Chondroblastoma was ruled out in this patient with physes still open. C and D, After 9 months of unsuccessful conservative treatment, arthroscopy and Herbert screw fixation were performed. At time of arthroscopy, lesion was hinged but attached. This procedure requires use of image intensifier for correct guide pin placement and to avoid the physis with the Herbert screws. E and F, Postoperative anteroposterior and lateral radiographs with Herbert screws in acceptable position.