Magnetic resonance images (MRI) were performed within three weeks of anterior cruciate ligament (ACL) rupture on 75 skeletally mature patients. Occult bony lesions were documented in 64 (85%) of the patients. Of the 64 patients with bone injuries, 83% had lesions of the lateral compartment. The lateral femoral condyle was involved in 50%, and the lateral tibial plateau was injured in 50% of the patients with changes. Nineteen of the 64 patients had more than one area of bony injury. Although the majority of bony lesions resolve, permanent alterations remained in some cases. This study has implications that may affect rehabilitation and the long-term prognosis in those patients with extensive bony and associated articular cartilage injuries.