Identifying Determinants of Asymmetrical Biomechanics During Single- and Double-Limb Countermovement Jumps 2 Years Following Anterior Cruciate Ligament Reconstruction.

After anterior cruciate ligament reconstruction (ACLR), individuals often demonstrate asymmetrical lower-extremity biomechanics and suboptimal vertical jump performance. These deficits have negative implications for reinjury risk and ability to return to sport. This study aims to quantify asymmetrical lower-extremity (hip, knee, and ankle) biomechanics and identify modifiable impairments contributing to altered knee joint mechanics and vertical jump performance after ACLR. Twenty-four individuals (19.6 [3.4] mo post-ACLR) performed isometric and isokinetic knee extensor strength testing followed by single- and double-limb vertical jumps using 3D motion capture. We found no differences in lower-extremity kinematics but did observe reduced peak knee extensor moment and joint power in the ACL-involved limb during both jumps. Furthermore, quadriceps peak torque and rate of torque development were significantly associated with propulsive knee joint power and vertical jump height. The findings from this study highlight that individuals demonstrate persistent knee joint underloading 2 years following ACLR that is related to inadequate quadriceps peak torque and rate of torque development. Clinicians should prioritize restoration of quadriceps peak torque and rate of torque development to improve knee joint kinetics, vertical jump performance, and overall readiness to return to competitive sport.