Joint Laxity Varies in Response to Partial and Complete Anterior Cruciate Ligament Injuries Throughout Skeletal Growth

Abstract Anterior cruciate ligament (ACL) injuries are increasingly common in skeletally immature populations. As such there is a need to increase our understanding of the biomechanical function of the joint following partial and complete injury during skeletal growth. In this work, we aimed to assess changes in knee kinematics and loading of the remaining soft tissues following both partial and complete ACL injury in a porcine model. To do so, we applied anterior-posterior tibial loads and varus-valgus moments to stifle joints of female pigs ranging from early juvenile to late adolescent ages and assessed both kinematics and in-situ loads carried in the bundles of the ACL and other soft tissues including the collateral ligaments and the menisci. We found increased translation and rotation of the joint following both partial and complete ACL injury, with complete ACL transection resulting in 2-fold increases in anterior-posterior tibial translation. At all ages, the medial collateral ligament and the medial meniscus combined to resist the majority of applied anterior tibial load following complete ACL transection. Across all ages and flexion angles, the contribution of the MCL ranged from 45-90% of the anterior load and the contribution of the medial meniscus ranged from 14-35% of the anterior load. These findings add to our current understanding of age-specific functional properties of both healthy and injured knees during skeletal growth.