Review of 25 proximal femora and 10 proximal tibiae of adolescent skeletons at the time of plate union reveals a distinct pattern of closure. The proximal femur initiates union superiorly with closure proceeding inferiorly. Closure of the tibia occurs along the anteromedial border and spreads posteriorly. No exceptions to these patterns were encountered. A knowledge of the pattern of plate union is useful when assessing fracture geometry in the injured adolescent and in trying to understand disorders of plate closure.