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

Background: Preventing 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. Methods: This 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). Results: The 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 perpendicular to 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. Conclusion: Dynamic 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. Copyright (c) 2013, Shanghai University of Sport. Production and hosting by Elsevier B.V. All rights reserved.