Joint Work Distribution During Single Leg Hop Landing After Anterior Cruciate Ligament Reconstruction

Prior work indicates that distance alone is not an adequate measure of movement quality in return to sport testing following anterior cruciate ligament reconstruction (ACLR); however, landing strategies and resulting differences in joint work contributions during single leg hop landings have been limited to homogenous ACLR cohorts. PURPOSE: This study assessed lower extremity joint work contributions during landing from a single leg hop for distance in ACLR patients > 6 months post-op. We hypothesized that the involved leg would show a shift in negative joint work from the knee to the hip as compared to the uninvolved limb, despite no measurable differences in hop distance. METHODS: 24 patients (M/F: 14/10; Age: 26 ± 9.2 y; Time Since Surgery: 41.2 ± 13.3 weeks), who underwent ACLR > 6 months prior to testing, were included in the analysis. Hop testing was conducted using a 10-camera motion capture system with two integrated force plates. Negative joint work was taken as the integral of the negative joint power curve from initial plate contact to three seconds after landing. Individual joint work was expressed as a percentage of total lower body work in this window. Paired t-tests were used to compare interlimb differences in joint work and hop distance with a Bonferroni-adjusted significance level of α = .01. RESULTS: Knee negative joint work contribution (MD±SE [CI95]: -9.54 ± 9.92 [-13.73, -5.35] %, p < .001, Cohen’s d: -0.961), total negative joint work (MD±SE [CI95]: -0.38 ± 0.64 [-0.65, 0.11] J/kg, p < .01, Cohen’s d: -0.599), and hop distance (MD±SE [CI95]: -0.14 ± 0.14 [-0.20, -0.08] m, p < .001, Cohen’s d: -0.979) were lower in involved compared to uninvolved limbs. Hip negative joint work contribution was larger in involved compared to uninvolved limbs (MD±SE [CI95]: 6.21 ± 9.75 [2.09, 10.33] %, p < .01, Cohen’s d: 0.637) while no differences in ankle joint work (p=.07) were detected. CONCLUSION: Single leg hop symmetry between limbs approached the necessary clinical criteria despite statistically significant differences in hop distances, rejecting the hypothesis that shifts in joint work occur without differences in hop distance. Alterations in lower extremity joint work were observed between the involved and uninvolved limbs of the heterogenous ACLR cohort > 6 months post-op indicative of altered landing strategies.