Optimizing Whole-Body Kinematics During Single-Leg Jump Landing to Reduce Peak Abduction/Adduction and Internal Rotation Knee Moments: Implications for Anterior Cruciate Ligament Injury Risk Dhruv Gupta, 1 Jeffrey A. Reinbolt, 1 and Cyril J. Donnelly 2,3 1 The University of Tennessee; 2 Nanyang Technological University; 3 The University of Western Australia Knee abduction/adduction moment and knee internal rotation moment are known surrogate measures of anterior cruciate ligament (ACL) load during tasks like sidestepping and single-leg landing. Previous experimental literature has shown that a variety of kinematic strategies are associated or correlated with ACL injury risk; however, the optimal kinematic strategies needed to reduce peak knee moments and ACL injury are not well understood. To understand the complex, multifaceted kinematic factors underpinning ACL injury risk and to optimize kinematics to prevent the ACL injury, a musculoskeletal modeling and simulation experimental design was used. A 14-segment, 37-degree-of-freedom, dynamically consistent skeletal model driven by force/torque actuators was used to simulate whole-body single-leg jump landing kinematics. Using the residual reduction algorithm in OpenSim, whole-body kinematics were optimized to reduce the peak knee abduction/adduction and internal/external rotation moments simultaneously. This optimization was repeated across 30 single-leg jump landing trials from 10 participants. The general optimal kinematic strategy was to bring the knee to a more neutral alignment in the transverse plane and frontal plane (featured by reduced hip adduction angle and increased knee adduction angle). This optimized whole-body kinematic strategy significantly reduced the peak knee abduction/adduction and internal rotation moments, transferring most of the knee load to the hip. Keywords: computational biomechanics, simulation, injury prevention, optimization, zero-moment-point computations Approximately 200,000 anterior cruciate ligament (ACL) injuries are documented in the United States each year. 1,2 With surgical reconstructions considered best clinician treatment, cou- pled with long rehabilitation periods (4–12 mo), ACL injuries cost the US health care system up to $1.5 billion USD annually. 3 The effects of ACL injuries are also severe to the injured athlete, as only 45% reach full recovery, 4 take as long as 2 years to reach the preinjury level of performance, 5 and are at a significantly higher risk of developing knee osteoarthritis within 10 years of their injury. 6 With the majority of ACL injuries being noncontact in nature, 7 many researchers and clinicians believe the most effective manner to reduce the burden of ACL injuries on society is through injury prevention (proactive) versus injury management (reactive) protocols. 8 The ACL load and injury risk is the greatest during the weight acceptance phase of the landing and sidestepping tasks. 9–11 The ACL load is elevated by anterior tibial forces in concert with abduction/adduction and internal rotation knee moments. 12–16 It is important to note that it is the combination of abduction/adduction and internal rotation knee moments that elevates the ACL load and injury risk more than either in isolation. 16 Therein, it should be the focus of injury-prevention frameworks to reduce both abduction/ adduction and internal rotation moments during the weight-accep- tance phase of single-leg landing and sidestepping if we are to effectively reduce ACL load, injury risk, and injury incidence in society. Researchers have investigated the effect different techni- ques, and postural combinations can have on peak knee abduc- tion/adduction moments during sidestepping and landing. Knee abduction/adduction moment has been correlated to sagittal 17 and nonsagittal plane knee kinematics, 18 knee range of motion, 19 hip kinematics, 15 foot strike posture, 20,21 trunk kinemat- ics, 14,17,18 arm kinematics, 13 and balance control. 22 These studies have helped establish associated links between different sporting techniques/postures, knee joint loading, and ACL injury risk; however, the complexity and interconnectedness of the multi- faceted system that is the human body has prevented researchers from making unified technique recommendations for reducing ACL injury risk in sport. To address this concern, Donnelly et al 11 used optimization methods with computer simulations to find optimal whole-body kinematics during the high-velocity sporting task of side stepping. They found that the general kinematic strategy to reduce the peak valgus knee moment during the sidestepping task was to redirect the whole-body center of mass toward the desired direction of travel. The absence of a foot contact model limits the interpretation and applicability of the results relating to the foot kinematics, which led to externally verifying this finding using a different popula- tion and experiment design. 20 Another noted limitation was reducing only the abduction/adduction knee moments without considering the internal rotation knee moment. Gupta and Reinbolt are with the Department of Mechanical, Aerospace, and Biomedical Engineering, The University of Tennessee, Knoxville, TN, USA. Donnelly is with the Rehabilitation Research Institute of Singapore, Nanyang Technological University, Singapore; and the School of Human Sciences, The University of Western Australia, Crawley, WA, Australia. Donnelly (cyril. donnelly@ntu.edu.sg) is corresponding author. 1 Journal of Applied Biomechanics, (Ahead of Print) https://doi.org/10.1123/jab.2020-0407 © 2021 Human Kinetics, Inc. ORIGINAL RESEARCH Brought to you by SUNG KYUN UNIV- MED LIB | Unauthenticated | Downloaded 09/23/21 03:53 AM UTC