Background: Retrograde nails are becoming used increasingly in the trauma setting and the indications are expanding. The goal of this study was to evaluate micromotion at fracture sites in the proximal half of the femur stabilized with a retrograde intramedullary nail to determine the effects of fracture location, canal fill, and screw configuration. Methods: Composite femurs were loaded in simulated single-leg stance while measurements of micromotion were made using linear variable differential