Knee abduction moment is predicted by lower gluteus medius force and larger vertical and lateral ground reaction forces during drop vertical jump in female athletes

Abstract

Prospective knee abduction moments measured during the drop vertical jump task identify those at increased risk for anterior cruciate ligament injury. The purpose of this study was to determine which muscle forces and frontal plane biomechanical features contribute to large knee abduction moments. Thirteen young female athletes performed three drop vertical jump trials. Subject-specific musculoskeletal models and electromyography-informed simulations were developed to calculate the frontal plane biomechanics and lower limb muscle forces. The relationships between knee abduction moment and frontal plane biomechanics were examined. Knee abduction moment was positively correlated to vertical (R = 0.522, P < 0.001) and lateral ground reaction forces (R = 0.395, P = 0.016), hip adduction angle (R = 0.358, P < 0.023) and lateral pelvic tilt (R = 0.311, P = 0.061). A multiple regression showed that knee abduction moment was predicted by reduced gluteus medius force and increased vertical and lateral ground reaction forces (P < 0.001, R² = 0.640). Hip adduction is indicative of lateral pelvic shift during landing. The coupled hip adduction and lateral pelvic tilt were associated to the increased vertical and lateral ground reaction forces, propagating into higher knee abduction moments. These biomechanical features are associated with ACL injury and may be limited in a landing with increased activation of the gluteus medius. Targeted neuromuscular training to control the frontal pelvic and hip motion may help to avoid injurious ground reaction forces and consequent knee abduction moment and ACL injury risk.

Introduction

Anterior cruciate ligament (ACL) tear is a serious sports injury. Approximately 250,000 ACL injuries occur each year in the United States (Johnson and Warner, 1993). While ACL reconstruction is the gold-standard procedure for athletes who return to sport after ACL injury, only 33–78% of young, reconstructed athletes are able to return to the same level of participation post-injury within a year (Ardern et al., 2011, Arundale et al., 2018, Geffroy, 2018). Especially, female athletes have a higher rate of ACL injury compared to male athletes (Stanley et al., 2016). Therefore, effective injury prevention and rehabilitation programs for female athletes are required to reduce ACL injury (Hewett and Bates, 2017). Females show larger external knee abduction moment measured in vivo during the drop vertical jump (DVJ) task relative to males (Ford et al., 2010), and the external knee abduction moment is a predictive factor of ACL injury in female athletes (Hewett et al., 2005). Externally applied knee abduction moment has also been identified as an injurious load as it induces anterior tibial translation (Bates et al., 2019, Matsumoto, 1990, Navacchia et al., 2019a, Ueno et al., 2020). Therefore, external knee abduction moment in female athletes is a targeted risk factor to be reduced in prevention programs (Sugimoto et al., 2015).

Knee abduction moment was correlated to lateral trunk tilt angle during side step cutting and single leg landing task (Dempsey et al., 2012, Jamison et al., 2012). The potential to decrease external knee abduction moment during landing by means of muscle activation has been shown with surface electromyography (EMG), but it is still controversial (Brown et al., 2014, Jamison et al., 2013, Palmieri-Smith et al., 2009). The relationships between net joint moment and EMG may be different among subjects because each subject may have different cross-sectional-area, firing rate and recruitment of motor units in a muscle to generate a joint torque. Unlike EMG data, musculoskeletal modeling provides muscle force magnitudes consistent with the joint moments calculated via inverse dynamics. A previous study reported that the force exerted by hip muscles, including the gluteus medius, gluteus maximus and piriformis, estimated with a static optimization method, primarily opposed the knee abduction moment during side-step-cutting (Maniar et al., 2018).

Musculoskeletal modeling is used to estimate muscle forces based on in vivo marker-based kinematics and ground reaction force (Laughlin et al., 2011, Maniar et al., 2018, Mokhtarzadeh et al., 2013, Navacchia et al., 2017, Navacchia et al., 2016, Ueno et al., 2017). However, the commonly used static optimization method is inadequate to estimate antagonist muscle activation during a co-contraction (Pizzolato et al., 2015). Novel approaches that use subject-specific EMG signals as inputs to the muscle force prediction, can now be utilized to estimate muscle forces consistent with subject-specific muscle activity (Afschrift et al., 2018, Pizzolato et al., 2015).

Direct collocation is a method to solve optimal control problems that has been recently used in biomechanics applications (De Groote et al., 2016). This technique discretizes and approximates continuous data using polynomial splines, which allows to simulate the dynamic equations of motion by solving all time frames simultaneously (Kelly, 2017). Consequently, muscle activations estimates are more consistent with muscle physiology compared to the static optimization method, as they account for the excitation-activation dynamics (De Groote et al., 2009). In addition, direct collocation requires shorter computational times compared to sequential shooting-based dynamic optimization approaches (De Groote et al., 2016, Kelly, 2017, Porsa et al., 2016). Furthermore, informing the objective function with subject-specific EMG data allow for an estimation of more physiological muscle co-contractions with respect to non-EMG-informed methods that minimize muscle activation (Navacchia et al., 2019b). An elevated co-contraction is produced by increased muscle forces in both agonist and antagonist forces compared to static optimization. This fact may provide different conclusions on the relationship between knee abduction moment and muscle forces compared to static optimization (Maniar et al., 2018).

Since hip muscles are the primary controllers of the trunk and hip position in a closed kinetic chain motion (Frank et al., 2013, Kim et al., 2016), higher hip abductor muscle activation are hypothesized to decrease the knee abduction moment during DVJ. Therefore, the purpose of this study was to determine the relationships between the knee abduction moment and lower limb muscle force during DVJ using an EMG-informed musculoskeletal model. Concurrently, the relationship between the knee abduction moment and frontal plane biomechanics, including vertical and lateral ground reaction force, hip adduction moment and trunk and hip kinematics were investigated, as a previous study indicated that those biomechanics variables might be related to the increased knee abduction moment during asymmetrical landing (Hewett and Myer, 2011). The hypothesis tested was that the knee abduction moment would be negatively correlated to the hip abductor muscle force and positively correlated to the vertical ground reaction force, lateral ground reaction force and lateral trunk lean.