Alterations In 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. During early stance, the quadriceps are the primary muscle group resisting knee joint collapse to allow preservation of upright posture. Gait strategies that shift loading from the knee 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. PURPOSE: To compare lower-limb support and inter-joint coordination during walking in those with ACLR. METHODS: Treadmill walking was evaluated in 27 individuals with ACLR (Sex: 16F, 11 M, Age: 23.5 ± 5.9 years, Time post-ACLR: 10.0 ± 1.4mo) at preferred speed. Sagittal ankle, knee, and hip moments during stance were extracted and the sum of the moments was used to calculate total support moment (TSM). Individual joint contribution (%) to the TSM was estimated at the time of 1st peak TSM. Inter-joint coordination was evaluated using a modified vector coding technique. Coupling angles were calculated for the ankle-knee and knee-hip during early (0-33%), mid (34-67%), and late (68-100%) stance. Paired t-tests compared TSM and joint contributions between-limbs (α = 0.05). Wilcoxon signed-rank tests compared coordination patterns (α = 0.05). RESULTS: We observed smaller 1st peak TSM in the ACLR limb (t = 2.89, p < 0.01). Knee and ankle contributions to 1st peak TSM were similar between limbs (p > 0.05), but hip contributions were 6% greater in ACLR limbs (t = 2.52, p = 0.02). The ACLR limb exhibited greater knee-hip anti-phase motion in early stance (z = 2.64, p < 0.01) but lesser in-phase motion in midstance (z = 4.25, p < 0.01). The ACLR limb exhibited greater isolated dorsiflexion between ankle-knee in early and midstance (z = 2.53 - 3.67, p < 0.05). CONCLUSIONS: Relative knee contributions to the 1st peak TSM were similar between limbs, but hip contributions were greater in the ACLR compared with contralateral limbs. This may be accomplished through small reductions in peak TSM and by modifying inter-joint coordination patterns to redistribute support demands. These adaptations in lower-limb coordination may shift the resultant force vector to lessen muscular requirements for support. F31 AR078592