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.