Association of the Single-Limb Hop Test With Isokinetic, Kinematic, and Kinetic Asymmetries in Patients After Anterior Cruciate Ligament Reconstruction

BACKGROUND: Asymmetries persist after anterior cruciate ligament reconstruction (ACLR). Physical performance tests such as the single-limb hop test have been used extensively to assess return-to-sport criteria, as they reproduce dynamic athletic maneuvers. HYPOTHESIS: The single-limb hop is associated with muscle strength and kinematic and kinetic asymmetries in ACLR patients 6 to 9 months after surgery. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-two men with ACLR (mean age, 28.8 ± 11.2 years) at 6 to 9 months (mean, 7.01 ± 0.93 months) after surgery completed isokinetic testing in 3 velocities (120, 180, and 300 deg/s) and a kinetic, kinematic, and functional evaluation of the single-limb hop test. Pearson correlation coefficients were used to assess the relationship between the Limb Symmetry Index (LSI) of the single-limb hop distance and each of the outcome variables. RESULTS: There were significant positive correlations between the LSI of the single-limb hop distance and the LSI of the peak extension torque at 120 deg/s (P = 0.044, r = 0.37) and the peak extension torque at 180 deg/s (P = 0.042, r = 0.38) as well as a negative correlation with the peak flexion torque at 180 deg/s (P = 0.043, r = −0.38). The LSI of the single-limb hop test was not correlated with any kinetic or kinematic variable (P > 0.05). CONCLUSION: The findings of the present study demonstrate that distance LSI of the single-limb hop test correlates with isokinetic extension peak torque LSI but not kinetic and kinematic asymmetry. CLINICAL RELEVANCE: The single-limb hop test can be used as an additional tool for the recognition of muscle strength asymmetries but not for kinetic or kinematic asymmetries 6 to 9 months after ACLR.