PAIN: NON-MALIGNANT DISEASES: Edited by Anthony H. Dickenson and Kirsty BannisterUpdate on pain in arthritisBharde, Sabah; Caxaria, Sara; Dell’Accio, Francesco; Sikandar, ShafaqAuthor Information William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, UK Correspondence to Shafaq Sikandar, William Harvey Research Institute: Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, UK. E-mail: [email protected] Current Opinion in Supportive and Palliative Care: June 2021 - Volume 15 - Issue 2 - p 99-107 doi: 10.1097/SPC.0000000000000551 Buy Metrics Abstract Purpose of review Osteoarthritis is a degenerative joint disease that features pain as a hallmark symptom. This review summarises progress and obstacles in our understanding of pain mechanisms in arthritis. Recent findings Pain phenotypes in osteoarthritis are poorly characterized in clinical studies and animal studies are largely carti-centric. Different animal models incur variable disease progression patterns and activation of distinct pain pathways, but studies reporting both structural and pain outcomes permit better translational insights. In patients, classification of osteoarthritis disease severity is only based on structural integrity of the joint, but pain outcomes do not consistently correlate with joint damage. The complexity of this relationship underlines the need for pain detection in criteria for osteoarthritis classification and patient-reported outcome measures. Summary Variable inflammatory and neuropathic components and spatiotemporal evolution underlie the heterogeneity of osteoarthritis pain phenotypes, which must be considered to adequately stratify patients. Revised classification of osteoarthritis at different stages encompassing both structural and pain outcomes would significantly improve detection and diagnosis at both early and late stages of disease. These are necessary advancements in the field that would also improve trial design and provide better understanding of basic mechanisms of disease progression and pain in osteoarthritis. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.