Inter-joint coordination and lower limb support in those with ACL-reconstruction

Individuals with anterior cruciate ligament reconstruction (ACLR) adopt altered walking patterns that shift support demands away from the surgical knee which may necessitate compensatory ankle or hip action to provide sufficient support. It is unclear how those with ACLR adapt and coordinate inter-joint motions to redistribute support demands during walking. Here, we compared lower-limb support and inter-joint coordination during walking in those with ACLR. Treadmill walking was evaluated in 28 individuals with ACLR and 20 healthy controls at preferred speed. The sum of sagittal joint moments in ankle, knee and hip was used to calculate total support moment (TSM) and individual joint contributions (%) to the TSM. Inter-joint coordination of ankle-knee and knee-hip was evaluated using a modified vector coding technique during early, mid and late stance. Paired t-tests compared TSM and joint contributions between-limbs (α = 0.05). Wilcoxon signed-rank tests compared coordination patterns (α = 0.05). We observed smaller 1st peak TSM in the ACLR limb (p < 0.01) and 6 % greater hip contributions in ACLR limbs (p = 0.02). We observed greater ankle motions in early and midstance, and greater hip motions in mid-late stance in ACLR limbs relative to comparison limbs. Overall, the ACLR limb exhibited coordination alterations characterized by increased reliance on ankle and knee motions to accommodate rigid knee mechanics throughout stance compared to non-ACLR and control limbs. Together, these joint coordination strategies may reduce and/or redistribute support demands in the ACLR limb to lessen muscular requirements for support and propulsion.