Bilateral Alterations in Running Mechanics and Quadriceps Function Following Unilateral Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Following anterior cruciate ligament reconstruction (ACLR), individuals have quadriceps muscle impairments that influence gait mechanics and may contribute to an elevated risk of knee osteoarthritis. OBJECTIVES: To compare running mechanics and quadriceps function between individuals who have undergone ACLR and those in a control group, and to evaluate the association between quadriceps function and running mechanics. METHODS: In this controlled, cross-sectional laboratory study, 38 individuals who previously underwent primary unilateral ACLR (mean ± SD time since reconstruction, 48.0 ± 25.0 months) were matched to 38 control participants based on age, sex, and body mass index, and underwent assessments of quadriceps muscle performance and running biomechanics. Quadriceps muscle performance was assessed via isokinetic and isometric knee extension peak torque and rate of torque development (RTD) over 2 time frames: 0 to 100 milliseconds (RTD100) and 0 to 200 milliseconds (RTD200). Running evaluation included assessment of the knee flexion angle (KFA), knee extension moment (KEM), rate of knee extension moment (RKEM), vertical instantaneous loading rate, and vertical impact peak. RESULTS: On average, there was a smaller KFA (P = .016) in the involved limb compared to the uninvolved limb in the ACLR group. Compared to limbs in the control group, involved limbs in the ACLR group had lower RTD100 (P = .015), lower peak torque at 60°/s (P = .007), lower peak torque at 180°/s (P = .016), smaller KFA (P<.001), lower KEM (P = .001), lower RKEM (P = .004), and higher vertical instantaneous loading rate (P = .016). Compared to limbs in the control group, uninvolved limbs in the ACLR group had lower RTD100 (P = .003), lower peak torque at 60°/s (P = .017), and smaller KFA (P = .01). For the involved limbs in the ACLR group, there was a low correlation between isokinetic peak torque at 180°/s and RKEM (r = 0.38, P = .01), and a negligible correlation between RTD100 and RKEM (r = 0.26, P<.05). No differences were found in isometric strength for any comparison. CONCLUSION: Individuals who have undergone ACLR have bilateral alterations in running mechanics that are weakly associated with diminished quadriceps muscle performance. J Orthop Sports Phys Ther 2018;48(12):960-967. Epub 22 Jul 2018. doi:10.2519/jospt.2018.8170.