Postural adaptations to unilateral knee joint hypomobility induced by orthosis wear during gait initiation

A Delafontaine,S Ditcharles,E Yiou,P Fourcade,J L Honeine

doi:10.1038/s41598-018-19151-1

Abstract

Balance control and whole-body progression during gait initiation (GI) involve knee-joint mobility. Single knee-joint hypomobility often occurs with aging, orthopedics or neurological conditions. The goal of the present study was to investigate the capacity of the CNS to adapt GI organization to single knee-joint hypomobility induced by the wear of an orthosis. Twenty-seven healthy adults performed a GI series on a force-plate in the following conditions: without orthosis (“control”), with knee orthosis over the swing leg (“orth-swing”) and with the orthosis over the contralateral stance leg (“orth-stance”). In orth-swing, amplitude of mediolateral anticipatory postural adjustments (APAs) and step width were larger, execution phase duration longer, and anteroposterior APAs smaller than in control. In orth-stance, mediolateral APAs duration was longer, step width larger, and amplitude of anteroposterior APAs smaller than in control. Consequently, step length and progression velocity (which relate to the “motor performance”) were reduced whereas stability was enhanced compared to control. Vertical force impact at foot-contact did not change across conditions, despite a smaller step length in orthosis conditions compared to control. These results show that the application of a local mechanical constraint induced profound changes in the global GI organization, altering motor performance but ensuring greater stability.

Highlights

Gait initiation (GI) is the transient phase between quiet standing posture and ongoing walking
The stance leg stiffness was computed along the mediolateral direction as follow: k = T/yCOM, where T, corresponded to an elastic restoring force that reflected the lateral control of the center of mass (COM) motion exerted by stance leg muscles, and yCOM corresponded to the COM shift, which
Swing knee mobility is involved in the maintenance of postural stability, with knee flexion at the end of anticipatory postural adjustments (APAs) contributing to the clearing of the swing foot from the ground and avoid stumbling

Summary

Introduction

Gait initiation (GI) is the transient phase between quiet standing posture and ongoing walking. Honeine et al.[8] reported that stance knee flexion during APAs, combined with ipsilateral hip adduction[16], would contribute to the anticipatory mediolateral COP shift and would be involved in the maintenance of postural stability. Restriction of knee mobility due to orthopedic impairments is commonly found in elderly[18], patients with knee arthritis[20] or wearing medical devices such as an orthosis; the most extreme case being that of upper knee amputees In this latter population, the strategy to control the forward propulsive forces to reach the intended motor performance has been shown to change in an adaptive manner according to the limb (sound or prosthetic) that initiated gait[19]. Recent studies reported that the central nervous system (CNS) in able-bodied participants was able to adapt mediolateral spatiotemporal features of APAs to various constraints imposed on the postural system, such as obstacles of changing height and distance[5], temporal pressure[5,6], fear of falling[27,28], speed instruction[29], asymmetrical body loading[30], and initial stance width[8] in order to maintain stability

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Conclusion