Langenskiold stages: Stage I : medio-distal beaking of the upper proximal tibial metaphysis. Stage II: wedging of the medial part of the upper tibial epiphyseal secondary ossification center plus a saucer shaped defect of the upper surface of the metaphyseal beak due to its dissolution, fragmentation & collapse. Stage III: stepping of the infero-medial border of the secondary ossification center but without extending distal to the physeal plate level plus deeping of the metaphyseal saucer into a step in the medial metaphysis. Stage IV: the epiphyseal secondary ossification center passes more distally and cross distal to the physeal level to fill the metaphyseal step. Stage V: separation of the most medial part of the ossification center from the bulk of the secondary ossification center and resides now in the depth of the metaphysiseal step below the physis. This is radiologically expressed as either a horizontal cleft (double epiphysis) or complete absence of the medial secondary ossification center as it will be overshadowed by the upper medial tibial metaphysis. Stage VI: medial epiphyseal plate closure with a bony bridge.