AB0978 Decreased pain and improved dynamic knee instability mediate the beneficial effect of wearing a soft knee brace on activity limitations in persons with knee osteoarthritis
Authors: T. Cudejko, M. van der Esch, J. van den Noort, J. Rijnhart, M. van der Leeden, L.D. Roorda, W. Lems, J. Harlaar, G. Waddington, J. Dekker
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> We have previously shown that wearing a soft knee brace reduced activity limitations in persons with knee osteoarthritis (OA).<sup>1</sup> Several underlying mechanisms have been proposed via which a soft knee brace reduces activity limitations in persons with knee OA.<sup>2</sup> However, to our knowledge, no study has identified mechanisms explaining this effect. <h3>Objectives</h3> The aim of the study was to identify mechanisms explaining the beneficial effect of wearing a soft knee brace on activity limitations in persons with knee OA. <h3>Methods</h3> This was an exploratory analysis of data from 44 participants with knee OA from Amsterdam Osteoarthritis cohort, who enrolled in a single-session within-subject cross-over design study, comparing a soft brace with no soft brace, and comparing a non-tight soft brace with a tight soft brace (GENUTEX A2, Human I). A mediation analysis was performed and the mediation effect was calculated based on the product of coefficients approach. Confidence intervals were calculated with a bootstrap procedure. The outcome measures were activity limitations assessed with the 10-metre walk test and the Get up and Go test. The studied mediators were the changes in: knee joint proprioception, pain, pressure pain threshold (PPT) and objective dynamic knee instability. Knee joint proprioception was assessed by the active movement extent discrimination assessment; pain with the Numeric Rating Scale (NRS); PPT with a hand-held pressure algometer, and dynamic knee instability with the Perturbation Response i.e. a measure reflecting deviation in the mean knee varus-valgus angle after a controlled mechanical perturbation on the treadmill, in respect to level walking. <h3>Results</h3> Both a decrease in pain during walking and a decrease in dynamic knee instability mediated the association between wearing a soft knee brace and reduction in time to complete both 10 m walk test and the GUG test (p&lt;0.05). Changes in proprioception and PPT did not mediate these associations (p&gt;0.05). Magnitudes of the mediation effects were similar for a non-tight and a tight soft knee brace. <h3>Conclusions</h3> The decrease in activity limitations in persons with knee OA who wear a soft knee brace might be explained by a decrease in self-reported pain and a reduction in dynamic knee instability. <h3>References</h3> [1] Cudejko T, van der Esch M, van der Leeden M, van den Noort JC, Roorda LD, Lems W, Twisk J, Steultjens M, Woodburn J, Harlaar J, Dekker J: The immediate effect of a soft knee brace on pain, activity limitations, self-reported knee instability, and self-reported knee confidence in patients with knee osteoarthritis. Arthritis Res Ther2017;19:260. [2] Cudejko T, van der Esch M, van der Leeden M, Roorda LD, Pallari J, Bennell KL, Lund H, Dekker J: Effect of Soft Braces on Pain and Physical Function in Patients With Knee Osteoarthritis: Systematic Review With Meta-Analyses. Arch Phys Med Rehabil2018;99:153–163. <h3>Disclosure of Interest</h3> None declared