Cross-education via contralateral-limb balance training improves gait speed and sagittal-plane knee motion after anterior cruciate ligament reconstruction: a randomized controlled trial

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Abstract

OBJECTIVE: This study examined whether contralateral-limb balance training, grounded in cross-education theory, enhances gait speed and reconstructed-knee kinematics during early postoperative recovery from anterior cruciate ligament reconstruction (ACLR). METHODS: A single-blind randomized controlled trial enrolled 40 patients 5-6 weeks post-ACLR, randomized 1:1 to an experimental group (n = 20; contralateral-limb balance training plus conventional rehabilitation) or a control group (n = 20; conventional rehabilitation alone), for 6 weeks (three sessions per week). Lower-limb kinematics during walking were captured using a Vicon three-dimensional motion-capture system, quantifying gait speed and knee-joint range of motion (ROM), peak angular velocity, and peak angular acceleration in the sagittal, coronal, and transverse planes. Data were analyzed using generalized estimating equations (GEE), with analysis of covariance (ANCOVA) examining whether gait-speed changes confounded the kinematic outcomes. RESULTS: The groups showed no baseline differences (all P > 0.05). Gait speed increased in both (both P < 0.001), with a significant time × group interaction favoring the experimental group (χ² = 11.98, P < 0.001; Hodges-Lehmann estimate 0.08 m/s, 95% CI 0.05-0.11). Sagittal-plane knee ROM likewise improved more in the experimental group (interaction χ² = 9.79, P = 0.002; mean difference 8.97°, 95% CI 5.40-12.54°; d = 1.61). No significant interactions emerged for coronal or transverse ROM, or for peak angular velocity or acceleration in any plane (all P > 0.05). ANCOVA showed that the sagittal-ROM advantage persisted after adjustment for gait-speed change (P = 0.002), indicating an independent benefit, whereas an apparent sagittal peak-angular-velocity advantage disappeared after adjustment (P = 0.165). Against available cross-population minimal clinically important difference (MCID) values (no ACLR-specific standards exist), the gait-speed difference fell below the multi-pathology range (0.10-0.20 m/s), whereas the sagittal-ROM difference exceeded the chronic-stroke reference (8.48°), although its 95% CI lower bound did not. CONCLUSION: Contralateral-limb balance training, as an adjunct to conventional rehabilitation, yielded greater improvements in gait speed and sagittal-plane knee ROM following ACLR, with the ROM benefit being independent of concurrent gait-speed gains. Kinematic gains were confined to the sagittal plane. Because the between-group differences did not consistently exceed existing MCID thresholds, these findings are statistically robust but of questionable clinical importance, necessitating larger studies and ACLR-specific MCID benchmarks. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR2400087325. Registered on 25 July 2024.

Abstract as published, via PubMed.