Background: Muscle weakness is characteristic of knee osteoarthritis. Muscle steadiness may be an important adjunct to knee muscle strength in improving physical function in knee osteoarthritis. However, the role of muscle steadiness is uncertain. Aims: To determine the associations of knee extensor muscle steadiness with maximal voluntary torque and physical function in patients with knee osteoarthritis. Methods: Baseline data from 177 patients in a randomized clinical trial were used. Isokinetic knee extension torque was processed into maximal voluntary torque [Nm]. Muscle steadiness was expressed as the coefficient of variance [%] and as peak power frequency [Hz]. Physical function was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index, the Get-Up-and-Go and Stair-climb tests. Associations were determined using regression analyses and adjusted for confounders. Findings: Lower muscle steadiness (i.e., higher coefficient of variance and peak power frequency) was associated with lower maximal voluntary torque (B = − 7.38, [−10.8, −3.95], R² = 0.10 and B = −14.71, [−28.29, −1.13], R² = 0.03, respectively). Higher coefficient of variance was associated with lower self-reported physical function (B = 1.14, [0.11,2.17], R² = 0.03) and remained significant after adjusting for potential confounders. Peak power frequency was not associated with physical function. Interpretation: Low muscle steadiness was weakly associated with low muscle strength and poorer self-reported physical function. Muscle steadiness and muscle strength seem to be different attributes of muscle function. There is no convincing evidence that muscle steadiness is an important adjunct in studying physical function in patients with knee osteoarthritis.

Objective: To evaluate whether improvement of proprioception, pain, or dynamic knee instability mediates the effect of wearing a soft knee brace on activity limitations in patients with knee osteoarthritis (OA). Methods: We conducted an analysis of data for 44 patients with knee OA who were enrolled in a laboratory-based trial evaluating the effect of wearing a commercially available soft knee brace. Activity limitations were assessed with the 10-meter walk test and the Get Up and Go test. Knee joint proprioception was assessed by an active joint position sense test; pain was assessed on a numeric rating scale (NRS) (range 0–10); pressure pain threshold (PPT) was assessed with a hand-held pressure algometer; dynamic knee instability was expressed by the perturbation response, i.e., a measure reflecting a deviation in mean knee varus–valgus angle after a controlled mechanical perturbation on a treadmill, with respect to level walking. Mediation analysis was conducted using the product of coefficients approach. Confidence intervals were calculated with a bootstrap procedure. Results: A decrease in pain (scored on an NRS) and a decrease in dynamic knee instability mediated the effect of wearing a soft knee brace on the reduction of activity limitations (P < 0.05), while changes in proprioception and PPT did not mediate this effect (P > 0.05). Conclusion: This study shows that decreased pain and reduced dynamic knee instability are pathways by which wearing a soft knee brace decreases activity limitations in patients with knee OA.

Objectives Wearing a soft knee brace has been shown to reduce self-reported knee instability in persons with knee OA. There is a need to assess whether a soft knee brace has a beneficial effect on objectively assessed dynamic knee instability as well. The aims of the study were to evaluate the effect of a soft knee brace on objectively assessed dynamic knee instability and to assess the difference in effect between a non-tight and a tight soft knee brace in persons with knee OA. Methods Thirty-eight persons with knee OA and self-reported knee instability participated in a laboratory study. A within-subject design was used comparing no brace vs brace and comparing a non-tight vs a tight brace. The primary outcome measure was dynamic knee instability, expressed by the perturbation response (PR). The PR reflects deviation in the mean knee varus-valgus angle during level walking after a controlled mechanical perturbation. Linear mixed-effect model analysis was used to evaluate the effect of a brace on dynamic knee instability. Results Wearing a brace significantly reduced the PR compared with not wearing a brace (B = -0.16, P = 0.01). There was no difference between a non-tight and a tight brace (B = -0.03, P = 0.60). Conclusion This study is the first to report that wearing a soft knee brace reduces objectively assessed dynamic knee instability in persons with knee OA. Wearing a soft brace results in an objective improvement of knee instability beyond subjectively reported improvement. Trial registration Nederlands Trial register (trialregister.nl) NTR6363

Background: We aimed to (i) evaluate the immediate effect of a soft knee brace on pain, activity limitations, self-reported knee instability, and self-reported knee confidence, and (ii) to assess the difference in effect between a non-tight and a tight soft brace in patients with knee osteoarthritis (OA). Methods: Forty-four patients with knee OA and self-reported knee instability participated in the single-session, laboratory, experimental study. A within-subject design was used, comparing a soft brace with no brace, and comparing a non-tight with a tight soft brace. The outcome measures were pain, self-reported knee instability and knee confidence during level and perturbed walking on the treadmill and activity limitations (10-m walk test and the get up and go (GUG) test). Linear mixed-effect model analysis for continuous outcomes and logistic generalized estimating equations for categorical outcomes were used to evaluate the effect of wearing a soft brace. Results: Wearing a soft brace significantly reduced pain during level walking (B - 0.60, P = 0.001) and perturbed walking (B - 0.80, P < 0.001), reduced the time to complete the 10-m walk (B - 0.23, P < 0.001) and the GUG tests (B - 0.23, P = 0.004), reduced self-reported knee instability during level walking (OR 0.41, P = 0.002) and perturbed walking (OR 0.36, P < 0.001), and reduced lack of confidence in the knees during level walking (OR 0.45, P < 0.001) and perturbed walking (OR 0.56, P < 0.001), compared with not wearing a soft brace. There was no difference in effects between a non-tight and tight brace, except for the 10-m walk test. Wearing a tight brace significantly reduced the time to complete the 10-m walk test in comparison with wearing a non-tight brace (B - 0.11, P = 0.03). Conclusion: The results of this study indicate that a soft brace is an efficacious intervention targeting pain, activity limitations, self-reported knee instability, and knee confidence in the immediate term in patients with knee OA. Further studies are needed evaluating the mode of action based on exerted pressure, and on the generalization to functioning in daily life. Trial registration: trialregister.nl, NTR6363. Retrospectively registered on 15 May 2017.