Elsevier

Gait & Posture

Volume 81, September 2020, Pages 21-26
Gait & Posture

Full length article
Influence of foot posture on immediate biomechanical responses during walking to variable-stiffness supported lateral wedge insole designs

https://doi.org/10.1016/j.gaitpost.2020.06.026Get rights and content

Highlights

  • Walking biomechanics at the knee and ankle differ with different insole properties.

  • Individuals with supinated feet exhibit less biomechanical changes with insoles.

  • Supported lateral wedge insoles re-distribute knee load while maintaining ankle kinetics.

  • Future work in people with knee osteoarthritis is justified.

Abstract

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.

Section snippets

Background

Lateral wedge insoles (LWI) are shoe-worn inserts that can alter walking biomechanics to conservatively manage knee osteoarthritis (OA). Specifically, LWI target reductions in the external knee adduction moment (KAM) – a surrogate measure of medial tibiofemoral compressive load [1]. Reducing the KAM is a primary goal of biomechanical interventions for knee OA, and a recent systematic review and meta-analysis reported that walking with LWI produces standardized mean differences between -0.20 and

Participants and foot posture groups

Healthy adults were recruited from the university and surrounding community via electronic and print media, and word of mouth. Participants were screened for, and excluded from, participation if they had any history of neurological conditions that may impair gait. In the twelve months prior to participation, participants were also free of any musculoskeletal pain or injury, and did not use orthotic insoles during this time. The six-item foot posture index (FPI) assessment [7] was used to

Results

Table 1 summarizes participant characteristics separated by foot posture groups, and Appendix 1 in Supplementary material summarizes frontal plane knee and ankle gait biomechanical outcomes.

Discussion

The current investigation explored novel designs of LWI and whether different foot postures would exhibit different biomechanical responses to these insoles. Five orthotic insole conditions – three of which included a LWI – were compared against a flat control insole. A reduction in the KAM was found only with the standalone LWI and one of the supported-LWI (WEDG + V-ARCH). The supported-LWI (WEDG + V-ARCH), however, minimized the increase in ankle/subtalar eversion moment compared to the LWI

Conclusions

The findings from this study suggest that supinated foot types respond differently than neutral and pronated foot types to various LWI designs, and subsequently may be less likely to respond biomechanically to these interventions. Supported-LWI using arch-support with a variable-stiffness design may be superior to a uniform-stiffness design for concurrently reducing magnitudes of the KAM while mitigating the increase in ankle/subtalar eversion moment compared to a LWI alone.

CRediT authorship contribution statement

Calvin T.F. Tse: Conceptualization, Methodology, Writing - review & editing, Investigation, Formal analysis, Writing - original draft, Visualization. Michael B. Ryan: Conceptualization, Methodology, Writing - review & editing, Supervision, Funding acquisition. Michael A. Hunt: Conceptualization, Methodology, Writing - review & editing, Supervision, Funding acquisition.

Declaration of Competing Interest

CT and MR are employed by Kintec Footwear + Orthotics, however, these authors do not receive any direct benefit from this research that could potentially bias these results. The authors declare no other profession or financial affiliations which would bias the results of this study.

Acknowledgments

The authors would like to thank Kintec Footwear + Orthotics for conducting the pedorthic assessments and for the fabrication of study orthotics. The authors would also like to thank Natasha Krowchuk for assistance in the data collection process. Study funding and salary support was provided by the Natural Sciences and Engineering Research Council of Canada, Canadian Institutes of Health Research, and the Michael Smith Foundation for Health Research.

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