Association between hip abductor function, rear-foot dynamic alignment, and dynamic knee valgus during single-leg squats and drop landings

BackgroundPreventing anterior cruciate ligament (ACL) injuries is very important for athletes, and dynamic knee valgus is considered a risk factor for non-contact ACL injury. However, little is known about whether the functions of the hip abductor and rear-foot increase dynamic knee valgus. A two-dimensional (2D) video-based screening test focused on hip abductor and rear-foot functions among factors involved in dynamic knee valgus. The present study determined associations between hip and rear-foot dynamic alignment and dynamic knee valgus.MethodsThis cross-sectional study recruited 130 female basketball players (258 legs) from nine high-school teams. The players performed single-leg squats and single-leg drop landings to provide knee-in (KID) and hip-out (HOD) distances on 2D video images. Hip and rear-foot dynamic alignment was evaluated using a dynamic Trendelenburg test (DTT) and a dynamic heel-floor test (HFT).ResultsThe Chi-square test revealed no significant difference in the prevalence of DTT-positivity between single-leg squats (28.7%) and single-leg drop landings (23.3%). The prevalence of HFT-positivity was significantly greater during landings (51.4%) than during single-leg squats (31.0%, p < 0.01). The KID values for both single-leg squats and single-leg drop landings were greater in the DTT-positive than in the DTT-negative group (15.1 ± 5.4 cm and 20.2 ± 7.5 cm, p < 0.001). The HOD values were similarly greater in the DTT-positive group (15.2 ± 1.9 cm and 17.6 ± 2.8 cm, p < 0.001). The KID values for both single-leg squats and single-leg drop landings were greater in the HFT-positive than in the HFT-negative group (12.2 ± 5.1 cm, p < 0.01; 14.7 ± 7.2 cm, p < 0.001), whereas HOD values for these tasks did not significantly differ between the two groups.ConclusionDynamic hip mal-alignment might be associated with both greater KID and HOD, whereas rear-foot eversion is associated only with greater KID. Hip abductor and rear-foot dysfunction are important factors for dynamic knee valgus and thus evaluating DTT and HFT will help to prevent dynamic knee valgus.