Diagnosis of trauma to the soft tissue structures of the knee such as menisci, cruciate ligaments, and collateral ligaments has been greatly advanced by MRI. Some bony lesions which couldnt be seen by simple X-rays, also became to be visualized by MRI. The authors reviewed 131 MRI s of traumatized knees from March, 1992 to August, 1995. Among them, various traumatic lesions of bone were found in 62 cases. Those cases were thoroughly reviewed to define the significances of the lesions, by reviewing the medical records and careful examination of simple X-rays and MRI. The bony lesions could be classified into four groups, such as coronal plane injuries (valgus, varus), sagittal plane injuries(contusion of proximal tibia-posterior cruciate ligament injury, patello-femoral contusions), nonspecific direct contusion, and tibial condylar fractures. In the valgus group, 3 components of MRI lesions as the evidences of valgus injury could be observed. They were direct contusions on lateral aspect of the knee, tension failure of medial aspect(medial collateral ligament injury), compression failure of lateral aspect of knee(focal compression lesions of femoral and/or tibial condyle adjacent to lateral meniscus). In other types of injuries, similar findings were observed as evidences of the events at the trauma. Most of the bony lesions were located at the sites where external forces were exerted and/or internal responses took place. It seems that bony lesions seen at MRI of traumatized knee are not simply meaningless, incidental findings but document the events at the time of the trauma.