Biomechanical asymmetries persist after ACL reconstruction: results of a 2-year study.

Purpose This study was aimed to examine longitudinal (6, 12, 18, 24 months) asymmetries in double-leg landing kinetics and kinematics of subjects with and without unilateral ACLR. Methods Three-dimensional kinematic and kinetic parameters of 40 participants (n = 20 post-ACLR, n = 20 healthy) were collected with a motion analysis system and force plate during a drop-landing task, and asymmetry indices were compared between groups. Results The asymmetry index (AI) in the ACLR group compared to the healthy group decreased from six to 24 months for vertical ground reaction force (vGRF) from 100% to 6.5% and for anterior posterior ground reaction force (a-pGRF) from 155.5% to 7%. Also, the AI decreased for peak hip flexion moment from 74.5% to 17.1%, peak knee flexion moment from 79.0% to 5.8% and peak ankle dorsiflexion moment from 59.3% to 5.9%. As a further matter, the AI decreased for peak hip abduction moment from 67.8% to 5.1%, peak knee adduction moment from 55.7% to 14.8% and peak knee valgus angle from 48.7% to 23.5%. Conclusions Results obtained from this longitudinal study showed that ACLR patients still suffer from limb asymmetries during landing tasks, which appear to normalize by 24-monthspost-surgery. This finding can help us to better understand biomechanics of the limbs after ACLR, and design more efficient post-surgery rehabilitation programs. Level of evidence Level III.