Quantitative initial safety range of early passive rehabilitation after ankle fracture surgery

•This study innovatively quantified the safety range of early passive rehabilitation training after ankle fracture surgery by finite element (FE) analysis.•The results of this study analyzed the influence of ankle flexion/extension on the internal mechanical environment after surgery.•This method has universality for any fracture that can be reconstructed. And this study provided the safety ranges of early rehabilitation training for six types of ankle fractures.