Load and Stride Increase Knee Adduction Velocity

Introduction: Service members often run at a fixed cadence with heavy body-borne loads (greater than 20 kg), which may lead to larger, faster knee adduction and risk of knee osteoarthritis. Although service members exhibit larger knee adduction walking with heavy load, it is unknown whether they use larger, faster knee adduction when running with load. Methods: Thirty-six participants had knee adduction quantified while running 4 m/s with four loads (20kg, 25kg, 30kg, 35kg) and three stride lengths (preferred, and 15% longer and shorter than preferred). For analysis, knee adduction angle and velocity were submitted to a RM ANOVA to test the main effect and interaction between body-borne load and stride. Results: Load and stride length had a significant effect on average velocity (p=0.050, p < 0.001) and time to peak for knee adduction (p=0.010, p<0.001), but only stride (p<0.001) impacted range of knee adduction. A significant load versus stride length interaction was observed for average varus thrust velocity (p=0.006), and both load and stride impacted magnitude of varus thrust (p=0.014; p < 0.001). Conclusion: Running with load and fixed cadence may elevate service member’s risk of knee OA, as increases in load and alterations in stride led to larger, faster knee adduction.