Background/Purpose: The aims of this study were to identify homogeneous subgroups of knee and/or hip osteoarthritis (OA) patients with distinct trajectories of the combination of pain, physical function (PF) and physical activity (PA) intensity) and to identify the baseline predictive factors associated with these trajectories.

Methods: The KHOALA cohort is a French population-based multicenter cohort of 878 patients with symptomatic knee and/or hip OA (ACR criteria), aged between 40 and 75 years old. Three outcomes assessed annually over 5 years were modeled in a multi-trajectory model. Pain and PF were measured with the WOMAC questionnaire while PA intensity (in Metabolic Equivalent of Task, MET) was assessed by the Modifiable Activity Questionnaire. First, trajectory models were estimated with varying number of groups for each of the outcomes separately and then, included in the multi-trajectory model. The selection of the optimal models was based on maximization of the Bayesian information criterion, the proportion of patients in each group (>5%) and the statistical significance of the equation modeled. Multinomial logistic regressions were performed to identify the predictive baseline characteristics associated with each group and were adjusted for sociodemographic and clinical factors.

Results: Comparison of separate trajectories of pain and PF showed that 2/3 of patients (66.7%) included in the trajectory of severe functional limitations (FL) also belonged to the more severe pain trajectory (Cramer V statistic = 0.59). Group-based multi-trajectory modeling revealed 3 distinct trajectories of pain, PF and PA intensity (Figure 1). The first (N=199, 32.1%) included patients with low pain levels, no FL and who practiced intense PA. The second (N=259, 41.8%) included patients with moderate levels of pain and FL; who practiced a less intense PA. Patients included in the third group (N=162, 26.1%) had severe pain, severe FL and a low-intensity practice. Overall, a decrease in PA intensity was observed in all groups over 5 years, even in the first group. In multivariate analyses, female sex (Odds ratio [OR]=2.93, 95% confidence interval [CI]=1.63-5.27),an increasing age (OR=1.04, 95%CI=1.01-1.08), a primary education level (OR=2.91, 95%CI=1.30-6.54), a high number of comorbidities (OR=1.50, 95%CI=1.23-1.83), a low vitality score (reflecting a high level of fatigue; OR=0.93, 95%CI=0.91-0.95) and a high Kellgren grade (reflecting a high radiological severity; OR=4.07, 95%CI=1.87-8.84) were associated with the third group membership.

Conclusion: Over 5 years, we identified 3 distinct trajectories combining pain, PF and PA intensity. The management of comorbidities and fatigue and slowing radiological progression seem important to maintain PF, limit pain and maintain intensity of PA practice in patients with symptomatic knee and/or hip OA.