Bone bruises represent a spectrum of occult bone lesions around the knee, which can only be detected by magnetic resonance imaging. These lesions can be isolated or are usually associated with other soft tissue injuries of the knee. These occult lesions are mostly associated with anterior cruciate ligament (ACL) injuries and are typically located in the lateral femoral condyle and the posterolateral tibial plateau. The location of the lesion may provide information on the mechanism of injury and associated soft tissue injuries. Bone bruises are less severe after low-energy trauma and most of these lesions usually regress within a short period. However, in lesions due to high-energy trauma like ACL injuries, healing may take years and those especially located close to the subchondral bone have the risk of associated osteochondral sequelae. Bone bruises may be responsible for the late degenerative changes of the knee after an ACL injury.