Impact Of Foot Progression Angle On Hip-knee Coordination During Cutting: Implications For ACL Injury Risk

Sport-specific movements, such as cutting, impose substantial demands on lower limb mechanics, placing athletes at high risk for anterior cruciate ligament (ACL) injuries. The alignment of the lower extremity during dynamic movements has emerged as a potential contributor to ACL injury risk. Among the factors influencing lower limb mechanics, foot progression angle (FPA) – defined as the angle between the foot and the line of progression – has been shown to alter knee mechanics during cutting. Additionally, FPA has been increasingly recognized as an influential factor in lower extremity coordination. While FPA’s impact on knee mechanics is well-documented, its influence on hip-knee coordination remains underexplored. Understanding FPA’s role in hip-knee coordination is essential given the coordination demands in dynamic sports. PURPOSE: To determine the effects of FPA on hip-knee coordination during cutting. METHODS: Twelve recreationally active females performed anticipated cutting tasks under three FPA angles: neutral, toe-in (15°), and toe-out (15°). Hip and knee joint coordination was analyzed using vector coding methods. Based on ACL loading mechanisms identified in the literature, the following intra-limb couplings of the stance limb were examined: hip (flexion/extension)-knee (flexion/extension), hip (rotation)-knee (flexion/extension), and hip (rotation)-knee(abduction/adduction). These couplings were compared across FPA conditions using paired sample t-tests (p ≤ 0.05). Cohen’s d effect sizes were also calculated. RESULTS: In-phase coordination with knee dominance (hip rotation/knee extension) was moderately greater in the neutral FPA compared to the toe-out FPA (p = 0.04; d = 0.52; 23 ± 11% and 18 ± 8% of stance, respectively). Anti-phase coordination with hip dominance (hip rotation/knee abduction) was moderately greater in the neutral FPA compared to the toe-in FPA (p = 0.049; d = 0.53; 13 ± 9% and 18 ± 10% of stance, respectively). No differences in coordination were observed for the other intra-limb couplings (p > 0.05). CONCLUSION: There is limited evidence to suggest that FPA affects lower limb coordination during anticipated cutting tasks. Future research is needed to investigate the influence of FPA on other intra-limb couplings and their implications on ACL injuries.