Back to normal symmetry? Biomechanical variables remain more asymmetrical than normal during jump and change of direction testing 9 months after anterior cruciate ligament reconstruction

Background Following anterior cruciate ligament reconstruction (ACLR), athletes have demonstrated performance asymmetries compared to healthy cohorts but little research has investigated if biomechanical asymmetries are also different during jump and change of direction (CoD) tasks between groups. Purpose To identify if differences in magnitude of asymmetry of biomechanical and performance variables exist between these groups. Study Design Case-Control Study Methods Analysis of 156 male subjects nine months after surgery and 62 healthy subjects was conducted. 3D motion capture and analysis was carried out on double leg drop jump (DLDJ), single leg drop jump (SLDJ), single leg hop for distance (SLHD) and planned and unplanned change of direction (CoD). Asymmetry between limbs was calculated for each variable using root mean square difference between limbs. Statistical parametric mapping was used to identify the between group differences in magnitude of asymmetry of performance and biomechanical variables. Results There were differences in asymmetry of biomechanical variables across all jump and CoD tests with greater asymmetries in the ACLR group. The majority of differences between groups were in the sagittal and frontal planes with more differences found in the jump than CoD tests. The SLDJ demonstrated large differences in performance asymmetry (effect size 0.94) with small differences for both CoD tests (0.4) and none for SLHD. Conclusion This study demonstrated greater asymmetry of biomechanical variables 9 months after ACL reconstruction compared to healthy subjects across all tests suggesting insufficient rehabilitation of normal symmetry. This highlights the importance of including biomechanical as well as performance variables when assessing rehabilitation status after ACLR.