Expanding and explaining symptoms in knee osteoarthritis trajectories: fluctuations, flares, and future directions.

Over the past decade, our understanding of knee osteoarthritis (OA) as a chronic long-term condition has evolved. Once primarily viewed as a chronic disease process of steady, inevitable decline, variations in the symptomatic course have now been demonstrated and replicated 1 Previtali D. Andriolo L. Di Laura Frattura G. Boffa A. Candrian C. Zaffagnini S. et al. Pain trajectories in knee osteoarthritis — a systematic review and best evidence synthesis on pain predictors. J Clin Med. 2020; 9: 2828 Crossref PubMed Scopus (23) Google Scholar . Group-based trajectory modeling, such as latent class growth models and growth mixture models, are data–driven processes designed to identify subgroups of people within longitudinal cohort datasets 2 Riddle D.L. Dumenci L. Modeling longitudinal osteoarthritis data to identify homogeneous subgroups: opportunities and challenges in a burgeoning literature. Osteoarthritis Cartilage. 2015; 23: 1035-1037 Abstract Full Text Full Text PDF PubMed Scopus (9) Google Scholar . The application of these approaches to knee OA pain has identified distinct subgroups demonstrating stable pain trajectories, ranging from mild to severe, worsening trajectories, and (for some) improving trajectories 3 Nicholls E. Thomas E. van der Windt D.A. Croft P.R. Peat G. Pain trajectory groups in persons with, or at high risk of, knee osteoarthritis: findings from the Knee Clinical Assessment Study and the Osteoarthritis Initiative. Osteoarthritis Cartilage. 2014; 22: 2041-2050 Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar . These studies have been pivotal in helping reframe the narrative about what it means to live with symptomatic OA.