The physeal injuries in children occur result of trauma, infection, metabolic or ischemic disease, and these conditions cause significant problems, such as growth disturbance, deformity and premature closure of physis. The authors experienced 7 cases of children who had angular deformity of knee and limb shortenings, but no history of obvious causes of physeal injury. All of these cases had severe osteoporosis and underlying disease, which were osteogenesis imperfecta, fibrous dyplasia and long term steroid therapy. The purpose of this study are evaluation of pathomechanism of physeal injuries in severe osteoporotic children. Patients were range of age from 4 to 9 years and had common clinical features, which were angular deformities of knee, limb shortening. Also they had common radiographic findings, that were severe porosis, metaphyseal sclerosis and in some cases, pop corn like calcification around physis. At this, we supposed that chronic mechanical stress in osteoporotic bone make physis be damaged due to loss of capillary circulation and this event appear to result from collapse of bone plate, through which epiphyseal vessel penetrate. In conclusion, the children with severe osteoporosis should be observed carefully about physeal injuries, which pathomechanism are perhaps deprivation of capillary circulation through bone plate. Therefore, We should try to protect bone plate by being conscious of its existence.