Effect of Running Speed on Knee Biomechanics in Collegiate Athletes Following Anterior Cruciate Ligament Reconstruction.

INTRODUCTION:Athletes post-anterior cruciate ligament reconstruction (ACLR) demonstrate altered surgical knee running kinematics and kinetics compared to the non-surgical limb and healthy controls. The effect of running speed on biomechanics has not been formally assessed in athletes post-ACLR. The purpose of this study was to characterize how knee biomechanics change with running speed between 3.5-7 (EARLY) and 8-13 (LATE) months post-ACLR. METHODS:Fifty-five Division I collegiate athletes post-ACLR completed running analyses (EARLY: n = 40, LATE: n = 41, both: n = 26) at 2.68, 2.95, 3.35, 3.80 and 4.47 m/s. Linear mixed effects models assessed the influence of limb, speed, time post-ACLR, and their interactions on knee kinematics and kinetics. RESULTS:A significant limb*speed interaction was detected for peak knee flexion, knee flexion excursion, and rate of knee extensor moment (p-values <0.02), controlling for time. From 3.35 to 4.47 m/s knee flexion excursion decreased -2.3° (95% CI: -3.6, -1.0) in the non-surgical limb and -1.0° (95% CI: -2.3, -0.3) in the surgical limb. Peak vertical ground reaction force, peak knee extensor moment, and knee negative work increased similarly with speed for both limbs (p-values <0.002). A significant limb*time interaction was detected for all variables (p-values <0.001). Accounting for running speed, improvements in all surgical limb biomechanics were observed from EARLY to LATE (p-values <0.001), except for knee flexion at initial contact (p = 0.12), but between-limb differences remained (p-values <0.001). CONCLUSIONS:Surgical and non-surgical knee biomechanics increase similarly with speed in collegiate athletes at EARLY and LATE, with the exception of peak knee flexion, knee flexion excursion, and rate of knee extensor moment. Surgical knee biomechanics improved from EARLY and LATE, but significant between-limb differences persisted.