A longitudinal investigation of landing biomechanics following anterior cruciate ligament reconstruction

ABSTRACT Objective Abnormal movement patterns have been shown during landing in patients who have undergone anterior cruciate ligament (ACL) reconstruction surgery. The purpose of this study was to investigate landing biomechanics over time in this patient group to determine whether asymmetry between limbs reduced with time and after a return to physical activity. Design Prospective longitudinal study Setting Biomechanics laboratory Participants Fourteen patients who had undergone ACL reconstruction surgery Main outcome measure Single limb landing assessments were made at two time points; within the first year (mean of 10 months) and at 3 years (after patients had returned to sport) following ACL reconstruction. Three-dimensional motion analysis was used to record kinematic and kinetic variables, which were compared across time and limb using ANOVA models. Results Most biomechanical variables showed little change over time except for the external knee adduction moment at the operated knee, which increased (effect size d=0.5), but remained less than the contralateral side. In the sagittal plane, asymmetrical landing patterns were seen at both assessments. Patients landed with reduced knee flexion angles (effect size range 0.76- 0.9) and moments (effect size range 0.56 – 0.9) compared to the uninjured limb and made compensations for this by increasing the hip flexion moment (effect size range d=0.6-0.75). Conclusions Asymmetrical landing biomechanics persisted at three years after ACL reconstruction in athletes who returned to sporting activity. Long term implications of controlling the landing by increasing the hip moment are unknown and require further investigation.