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Within-subject foot motion variability in patients with Rheumatoid Arthritis


Multi-segment three-dimensional analysis is a complex yet rapidly evolving methodology in podiatric mechanical research. The purpose of this study was to explore the within-subject foot motion variability (MoVa) during the stance phase of gait.


A 3D motion analysis system was used to collect gait data for 5 healthy participants and 5 patients with RA. The oxford foot model was used to characterise dynamic foot & ankle kinematics and spatio-temporal parameters. Inter-segmental motions of interest were defined as tibia-rearfoot and rearfoot-forefoot. The main outcome of interest was within-subject MoVa, expressed as mean standard deviation (SD).


MoVa ranged from 0.94- 2.33SD and was similar for both groups. Increased MoVa was largely accounted for by rearfoot variance. There is a trend towards increased forefoot MoVa in the RA group (RA 0.65-1.78, Control 0.34-0.9). No single episode during the stance phase had greater variability than any other.


MoVa rather than a particular gait event may be an alternative outcome warranting further investigation. These results suggest care should be taken when assuming mean within-subject MoVa in mechanical analyses. This preliminary work suggests that greater forefoot MoVa may occur in RA participants. This pilot investigation provides useful preliminary data to inform future studies.

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This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Hooper, L., Gates, L., Goulston, L. et al. Within-subject foot motion variability in patients with Rheumatoid Arthritis. J Foot Ankle Res 3 (Suppl 1), P7 (2010).

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