Bone bruise or occult osseous lesion on magnetic resonance imaging was focused on the indirect sign of acute anterior cruciate ligament injury. But there were few reports which compared the location of bone bruise with the injured structure. The purposes of this study were to identify the common pattern of location of bone bruise, and to analyze the relationship between the location and injured structure or mechanism of injury. The authors reviewed 76 magnetic resonance imaging studies of the knee from March 1993 to May 1994 which show the sign of bone bruise in acute knee injury within six weeks. The mean age of the patient was 26.3 years and the main cause of injury was traffic accident. The final diagnosis was 20 cases of isolated medial collateral ligament injury, 17 cases of isolated anterior cruciate ligament injury, 16 cases of combined anterior cruciate and medial collateral ligament injury, 7 cases of meniscus injury, 6 cases of combined posterior cruciate and medial collateral ligament injury, 5 cases of isolated posterior cruciate ligament injury, 2 cases of patella dislocation, 1 case of lateral collateral ligment injury, and 2 cases of undiagnosed knee injury. In isolated MCL injuries, bone bruises were all confined to the lateral compartment. In isolated injury of ACL, the most common pattern of location of bone bruises were lateral tibial plateau and lateral femoral condyle(47.1%). In combined ACL and MCL injury, the most common pattern of location was lateral tibial plateau, only(43.8%). Bone bruise on MRI may be easy to detect during interpretation and we can obtain much information to decide the diagnosis and prognosis.