Association between seated postural control and gait speed in knee osteoarthritis.

The purpose of this study was to evaluate, in patients with knee osteoarthritis, whether seated postural control is a multivariate predictor of gait speed, after adjusting for the effects of conventional knee impairments. Sixty-seven patients with knee osteoarthritis awaiting total knee replacement participated. To measure seated postural control, patients sat on a balance board, and the centre-of-pressure (COP) measures calculated in the anterior-posterior (AP) and medio-lateral (ML) directions were standard deviation (SD) and mean frequency (MF). Isometric knee extensor strength was measured using an isokinetic dynamometer; knee flexion range-of-motion, an extendable goniometer; and knee pain intensity, a numeric pain rating scale. Fast-pace gait speed was assessed by the 10-m walk test and a poor gait speed was defined at a cutoff value of 1.0m/s. At the univariate level, the seated COP measures, with the exception of AP-MF, discriminated between patients with and without poor gait speed; however, only ML-MF retained its predictive value in multivariable analyses adjusted for demographic, anthropometric, and knee impairment measures. These findings suggest that seated postural control may be an important correlate of physical function in patients with knee OA and that greater emphasis in the assessment of trunk control may be warranted in this population.