Influence of foot posture on immediate biomechanical responses during walking to variable-stiffness supported lateral
Calvin T F Tse1, Michael B Ryan2, Michael A Hunt3
1Graduate Programs in Rehabilitation Sciences, University of British Columbia, 2211 Wesbrook Mall, Vancouver, BC V6T 1Z7, Canada; Motion Analysis and Biofeedback Laboratory, University of British Columbia, 212 - 2177 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada; Kintec Footlabs, 13645 King George Blvd., Surrey, BC V3T 2TB, Canada.
Background:
Novel designs of lateral wedge insoles with arch support can alter walking biomechanics as a conservative treatment option for knee osteoarthritis. However, variations in foot posture may influence individual responses to insole intervention and these effects are not yet known.
Research Question:
How does foot posture influence biomechanical responses to novel designs of lateral wedge insoles with arch support?
Methods:
This exploratory biomechanical investigation categorized forty healthy volunteers (age 23-34) into pronated (n = 16), neutral (n = 15), and supinated (n = 9) foot posture groups based on the Foot Posture Index. Three-dimensional gait analysis was conducted during walking with six orthotic insole conditions: flat control, lateral wedge, uniform-stiffness arch support, variable-stiffness arch support, and lateral wedge + each arch support. Frontal plane knee and ankle/subtalar joint kinetic and kinematic outcomes were compared among insole conditions and foot posture groups using a repeated measures analysis of variance.
Results:
The lateral wedge alone and lateral wedge + variable-stiffness arch support were the only insole conditions effective at reducing the knee adduction moment. However, the lateral wedge + variable-stiffness arch support had a smaller increase in peak ankle/subtalar eversion moment than the lateral wedge alone. Supinated feet had smaller ankle/subtalar eversion excursion and moment impulse than neutral and pronated feet, across all insole conditions.
Significance:
Supinated feet have less mobile ankle/subtalar joints than neutral and pronated feet and, as a result, may be less likely to respond to biomechanical intervention from orthotic insoles. Supported lateral wedge insoles incorporating an arch support design that is variable-stiffness may be better than uniform-stiffness since reductions in the knee adduction moment can be achieved while minimizing increases in the ankle/subtalar eversion moment.
