The authors report a case of an undiagnosed Kocher-Lorenz fracture in a 12-year-old adolescent. The Kocher-Lorenz type fracture involves a superficial osteochondral shell of the capitellum with little underlying bone. Three years after trauma, the patient still complained of throbbing and occasional elbow pain. Radiographic examination revealed a large intra-articular bone fragment mimicking the shape of a “second radial head”, between the lateral condyle’s ossification center and the radial head. Surgical treatment by fragment excision was performed. Eight years postoperatively, the patient had fully recovered with complete relief of pain. The patient demonstrated full range of motion in all planes. The authors offer a review of the literature on this rare fracture which diagnosis is often delayed.