The golf ball sign: arthroscopic localization of an osteochondritis dissecans lesion of the knee.

We report on the arthroscopic treatment of a 12-year-old boy diagnosed with an osteochondral defect of the medial femoral condyle. He underwent arthroscopic fixation of the defect, and during the surgery, a blunt trocar was used to localize the lesion. The trocar created a transient dimpling effect on the cartilage overlying the osteochondral defect that resembled the surface of a golf ball. This "golf ball sign" then served as a visual guide during placement of a chondral dart. When present, it is believed that this sign can benefit arthroscopists by helping to improve intraoperative localization of an osteochondral defect.