Influence of Foot-Landing Positions at Initial Contact on Knee Flexion Angles for Single-leg Drop Landings

Purpose: Small knee flexion angles are associated with increased non-contact anterior cruciate ligament (ACL) injury risks. The purpose of this study was to provide insights into how ankle plantar flexion angles influenced knee flexion angles at initial contact during single-leg drop landings. Method: Thirteen male recreational basketball players performed single-leg drop landings from a 30-cm high platform using three randomized foot-landing positions (natural, fore-foot, and flat-foot). A motion capture system and a force plate were used to measure lower extremity kinematics and vertical ground reaction force (VGRF). A one-way repeated measures Analysis of Variance and the Friedman test were conducted (alpha = .05). Results: Foot-landing position had a significant effect on knee flexion angles at initial contact (p < .001). As compared to flat-foot landings (18 degrees (SD 5 degrees), significantly smaller knee flexion angles were found for natural (mean 12 degrees (SD 5 degrees), p = .004) and fore-foot landings (mean 12 degrees (SD 3 degrees), p = .001). There was however significantly smaller knee flexion range of motion in flat-foot landings (mean 42 degrees (SD 3 degrees), as compared to natural landings (mean 48 degrees (SD 4 degrees) (p < .001). Flat-foot landings also resulted in a 1.4 times higher maximum VGRF than fore-foot landings (p < .001) and 1.3 times higher than natural landings (p = .005). Conclusions: Natural and fore-foot landings are better for force absorption but are associated with smaller knee flexion angles at initial contact. These findings have important implications for non-contact ACL injuries.