Abstract
Background Non-contact anterior cruciate ligament (ACL) injuries commonly occur when athletes land in high risk positions such as knee valgus. The position of the foot at landing may influence the transmission of forces from the ankle to the knee. Using an experimental approach to manipulate foot rotation positions, this study aimed to provide new insights on how knee valgus during single-leg landing may be influenced by foot positions.
Methods Eleven male recreational basketball players performed single-leg drop landings from a 30-cm high platform in three foot rotation positions (toe-in, toe-forward and toe-out) at initial contact. A motion capture system and a force plate were used to measure lower extremity kinematics and kinetics. Knee valgus angles at initial contact (KVA) and maximum knee valgus moments (KVM), which were known risk factors associated with ACL injury, were measured. A one-way repeated measures Analysis of Variance was conducted (α = 0.05) to compare among the three foot positions.
Results Foot rotation positions were found to have a significant effect on KVA (p < 0.001, η2 = 0.66) but the difference between conditions (about 1°) was small and not clinically meaningful. There was a significant effect of foot position on KVM (p < 0.001, η2 = 0.55), with increased moment observed in the toe-out position as compared to toe-forward (p = 0.012) or toe-in positions (p = 0.002).
Conclusions When landing with one leg, athletes should avoid extreme toe-out foot rotation positions to minimise undesirable knee valgus loading associated with non-contact ACL injury risks.
1. Introduction
Anterior cruciate ligament (ACL) injuries commonly occur during sports such as basketball, soccer, and Australian Football [1,2]. These injuries may result in long absence from play [3] and thus negatively impact the careers of athletes. ACL injuries often happen in manoeuvres such as sidestepping and single-leg landing during non-contact situations [4], in which players are not hit by an object or another player [1]. Instead, from the video analyses of ACL injuries, athletes frequently land in high risk positions such as knee valgus positions [5–7] whereby one or both knees are seen moving towards the midline of the body [8]. In the prospective cohort study of female athletes by Hewett et al. [9], athletes who sustained ACL injuries landed at higher knee valgus angles (KVA) at initial contact during a drop vertical jump.
5. Conclusions
This study showed that foot rotation positions can influence knee joint loading during single-leg drop landing. Specifically, landing in toe-out positions resulted in significantly higher maximum KVM compared with toe-in and toe-forward positions. Although foot rotation positions also influenced KVA at initial contact, the differences were too small to be clinically meaningful. When landing with one leg, athletes should avoid extreme toe-out foot rotation positions to minimise undesirable knee valgus loading associated with non-contact ACL injury risks.
