Association Between Anatomical Characteristics, Knee Laxity, Muscle Strength, and Peak Knee Valgus During Vertical Drop-Jump Landings

Study Design Controlled laboratory study; cross-sectional. Objectives To investigate the relationship among anatomical variables, knee laxity, muscle strength, and peak knee valgus angles during a vertical drop-jump landing task. Background Excessive knee valgus has been associated with anterior cruciate ligament injury in females; however, the influence of anatomical characteristics, knee laxity, and muscle strength on frontal plane knee motion is not completely understood. Methods Norwegian elite female soccer players (n = 279; mean ± SD age, 21 ± 4 years; height, 167 ± 6 cm; body mass, 63 ± 7 kg) were evaluated from 2009 through 2012. The evaluation included 3-D motion analysis of a vertical drop jump, anatomical measures (height, static knee valgus, leg length, and static foot posture), knee laxity, and muscle strength (quadriceps, hamstrings, and hip abductors). Multiple linear regression analyses were used to investigate the relationships among anatomical characteristics, knee laxity, muscle strength, and peak knee valgus angles. Results Anatomical characteristics explained 11% of the variance in peak knee valgus angles (P<.001), with height and static knee valgus being significant predictors. Conclusion Greater body height and static knee valgus were associated with greater peak knee valgus angles during a vertical drop-jump landing task. However, these variables only explained 11% of the variance in peak knee valgus.