Gait asymmetry as a determinant of functional recovery and return to sport after ACL reconstruction: a cross-sectional biomechanical analysis

Abstract

Introduction Gait asymmetry and impaired functional performance are common after anterior cruciate ligament (ACL) reconstruction and may influence return-to-sport (RTS) outcomes. Despite advancements in rehabilitation, a substantial proportion of individuals fail to regain pre-injury activity levels, often due to unresolved biomechanical deficits. Quantifying gait asymmetry and its relationship with functional capacity may provide insight into factors that differentiate those who successfully return to sport from those who do not. Methods Eighty-six participants (43 RTS, 43 non-RTS) between 6 and 24 months post-ACL reconstruction completed 3D gait analysis and a standardized battery of single-leg hop tests. Gait asymmetry indices included kinetic and kinematic variables, while functional performance was assessed using hop distances, timed hops, and limb symmetry indices (LSIs). Group comparisons were analyzed using independent t -tests, and relationships were examined using Pearson correlations and multiple linear regression. Results The RTS group demonstrated significantly lower asymmetry across all gait variables, including vertical ground reaction force asymmetry expressed as an asymmetry index percentage derived from body-weight–normalized force values (8.45% ± 3.21% vs. 12.34% ± 4.02%, p = 0.001) and peak knee flexion angle asymmetry (degrees; 3.12 ± 1.10° vs. 5.67 ± 1.45°, p < 0.001). They also performed better on all hop tests, including single-leg hop distance (centimeters; 162.34 ± 12.45 vs. 148.76 ± 14.33 cm, p < 0.001) and Limb Symmetry Index for the 6-m timed hop (percentage ratio of involved-to-uninvolved limb performance; 96.45% ± 2.85% vs. 88.34% ± 3.65%, p < 0.001). Gait asymmetry metrics showed moderate-to-strong correlations with hop performance (r = −0.58 to 0.44). Regression analysis identified peak knee flexion angle asymmetry (B = −2.45, β = −0.41, p < 0.001) and knee extensor moment asymmetry (B = −8.12, β = −0.39, p = 0.004) as significant predictors. Conclusion Gait asymmetry differentiates individuals based on RTS status and significantly predicts functional performance after ACL reconstruction. These findings support the clinical integration of gait analysis to guide rehabilitation and RTS decisions.