Increased Gait Speed Changes Knee Mechanics Following Anterior Cruciate Ligament Reconstruction: Implications and Caution for Treadmill Training in Early Rehabilitation.

Abstract

Background: Current rehabilitation practices following anterior cruciate ligament reconstruction (ACLr) do not guarantee recovery of gait mechanics suggesting that gait specific interventions are needed. Increasing gait speed implicitly increases lower extremity demands; however, it is not known if increased treadmill speed will result in improved knee mechanics in early recovery post-ACLr. Therefore, the purpose of this study was to determine how individuals four months post-ACLr respond to the demands of increased speed during treadmill gait.

Study design: Cross-sectional.

Methods: Ten individuals 109.2±19.9 days post-ACLr and twelve uninjured individuals participated. Participants walked on a treadmill at self-selected (SS), 25% faster (SS25) and 50% faster (SS50) speeds. Kinematic and kinetic data were used to calculate net joint moments using standard inverse dynamic equations. Knee power was calculated as the scalar product of angular velocity and sagittal plane net joint moment. Knee flexion excursion was calculated from initial contact to the subsequent knee flexion peak. A 3 X 2 ANOVA assessed the effect of group and speed (SS, SS25, SS50) on surgical (or control) knee extensor moment, power absorption, knee excursion, GRFs and between limb symmetry.

Results: For controls, knee extensor moment, power absorption, excursion, and GRFs increased at each speed. For ACLr, knee loading variables increased between SS to SS25 without changes in limb symmetry. No further increase in knee moments were observed between SS25 and SS50, but limb symmetry decreased in extensor moment, power, and GRFs.

Conclusion: At four months post-ACLr, a moderate increase in treadmill speed may provide a stimulus to improve knee loading without increased asymmetries. Larger increases in speed should be exercised with caution to avoid undesirable between limb compensations. A progressive increase in demand to improve knee loading deficits during early recovery of ACLr is warranted.

Level of evidence: 2.