Hop Distance Symmetry Does Not Indicate Normal Landing Biomechanics in Adolescent Athletes With Recent Anterior Cruciate Ligament Reconstruction.

Background Return-to-sport protocols after anterior cruciate ligament reconstruction (ACLR) often include assessment of hop distance symmetry. However, it is unclear whether movement deficits are present, regardless of hop symmetry. Objectives To assess biomechanics and symmetry of adolescent athletes following ACLR during a single-leg hop for distance. Methods Forty-six patients with ACLR (5-12 months post surgery; 27 female; mean ± SD age, 15.6 ± 1.7 years) were classified as asymmetric (operative-limb hop distance less than 90% that of nonoperative limb [n = 17]) or symmetric (n = 29) in this retrospective cohort. Lower extremity biomechanics were compared among operative and contralateral limbs and 24 symmetric controls (12 female; mean ± SD age, 14.7 ± 1.5 years) using analysis of variance. Results Compared to controls, asymmetric patients hopped a shorter distance on their operative limb (P<.001), while symmetric patients hopped an intermediate distance on both sides (P≥.12). During landing, the operative limb, regardless of hop distance, exhibited lower knee flexion moments compared to controls and the contralateral side (P≤.04), with lower knee energy absorption than the contralateral side (P≤.006). During takeoff, both symmetric and asymmetric patients had less hip extension and smaller ankle range of motion on the operative side compared with controls (P≤.05). Asymmetric patients also had lower hip range of motion on the operative, compared with the contralateral, side (P = .001). Conclusion Both symmetric and asymmetric patients offloaded the operative knee; symmetric patients achieved symmetry, in part, by hopping a shorter distance on the contralateral side. Therefore, hop distance symmetry may not be an adequate test of single-limb function and return-to-sport readiness. J Orthop Sports Phys Ther 2018;48(8):622-629. Epub 30 Mar 2018. doi:10.2519/jospt.2018.7817.