Effects of modifiable footwear features on anterior cruciate ligament force in young females during a drop-lateral-jump task

Purpose: Aberrant lower limb biomechanics of young females contribute to elevated knee loads and a susceptibility to non-contact anterior cruciate ligament (ACL) injury. Specific design features of athletic footwear may alter impact-related loads transferred up the kinetic chain to the knee. This cross-sectional biomechanical study examined the effects of modifiable footwear design features (heel height/pitch and medial arch support) on ACL force-time parameters of females during single-limb landing. Methods: Fifty-two healthy late/post-pubertal females (Tanner stage IV-V) performed a single-limb drop-lateral-jump (DLJ) task in nine footwear conditions, with different combinations of shoe pitch (4 mm, 7 mm and 10 mm) and medial arch support (no support, low support and high support). Using three-dimensional joint kinematics, ground-reaction forces, and electromyography (EMG) data, an EMG-informed neuromusculoskeletal computational model predicted ACL force during the weight-acceptance phase of the DLJ task. A mixed effects linear regression model was used to compare the magnitude and temporal characteristics of ACL force between footwear conditions. Tukey’s post-hoc comparisons were conducted for significant ( p <0.05) main effects or interactions. Results: For peak ACL force, no significant main effect or interaction was found. A significant main effect of shoe pitch was found for time-to-peak ACL force ( p <0.001), where the 4mm shoe pitch delayed time-to-peak by 3.23ms and 4.28ms compared to the 7mm ( p <0.001) and 10mm ( p <0.001) conditions, respectively. Conclusion: Although a delayed time-to-peak ACL force was observed with the 4mm shoe pitch condition, the relatively small temporal differences observed, and the fact that peak ACL force did not differ across pitch variants, suggest that these findings may have few real-world implications.