Longitudinal associations between bilateral versus unilateral knee osteoarthritis and physical performance measures

Background: Bilateral knee osteoarthritis (KOA) is common, but evidence for the effect of bilateral versus unilateral KOA on functional outcomes is conflicting. We aimed to examine the association between bilateral versus unilateral KOA and physical performance measures over two years. Methods: Our cohort included adults with symptomatic, radiographic KOA. Study assessments at baseline, 12 and 24 months included the 30-s chair sit-to-stand task (CST) and 40-m walk (40 ​MW). We defined bilateral KOA as Kellgren-Lawrence grade ≥2 and Knee Osteoarthritis Outcome Pain Scale ≥17/100 in both knees. We used linear mixed models to (1) assess the cross-sectional association between the presence of bilateral versus unilateral KOA at each timepoint and performance measures, and (2) assess the association between bilateral versus unilateral KOA at baseline and longitudinal changes in performance measures. Models were adjusted for clinical and demographic covariates. Results: 101 participants were included. At baseline, 43/101 (43 ​%) had bilateral KOA. In adjusted models, bilateral, versus unilateral, KOA was associated with 1.0 fewer stands on the CST (95 ​% CI: 2.2–0.1), and a 0.03 ​m/s slower 40 ​MW (95 ​% CI: 0.10–0.04). Average 2-year change in CST was −0.6 stands in those with baseline bilateral KOA and −0.7 in those with unilateral KOA (between-group difference, 0.1 stands (95 ​% CI: 1.7–1.8)). The baseline bilateral KOA group had greater worsening in 40 ​MW time (between-group difference −0.10 ​m/s (95 ​% CI: -0.20–0.00)). Conclusions: We did not find clinically significant associations between bilateral vs unilateral KOA and performance on two physical performance tasks over two years of follow-up in this cohort study.