Lower-Limb Joint Work Redistribution and Altered Movement Control During Double-Leg Squatting in Patients 6 Months After Anterior Cruciate Ligament Reconstruction

Individuals undergoing anterior cruciate ligament reconstruction (ACLR) remain at risk of secondary injury and joint degeneration, highlighting the need for functional assessments that detect abnormal load regulation and compensatory movement strategies. This study compared lower-limb kinematics, kinetics, and joint work contributions during double-leg squatting between 27 patients 5.9 ± 0.7 months after ACLR and 23 healthy controls. Three-dimensional marker trajectories and ground reaction forces were collected, and biomechanical variables were analyzed using a two-way mixed-design ANOVA. The reconstructed limb showed smaller knee flexion angles and lower knee extensor moments than both the contralateral limb and the non-dominant limb of healthy controls (p ≤ 0.015), together with reduced ankle dorsiflexion and peak vertical ground reaction force versus the contralateral limb (p < 0.001). Compared with healthy controls, the ACLR group also showed altered frontal- and transverse-plane hip and knee mechanics (p ≤ 0.017). The reconstructed limb demonstrated greater negative hip work and hip work contribution, lower negative knee work and knee work contribution (all p ≤ 0.003), and greater ankle work contribution than the contralateral limb (p = 0.018). These findings describe a cross-sectional biomechanical pattern at approximately 6 months after ACLR characterized by sagittal-plane knee control deficits, bilateral hip control differences, and altered inter-joint work distribution.