159 Self-report central mechanisms trait predicts knee pain persistence in the Knee Pain In the Community (KPIC) cohort Free

Background: In the UK, approximately 25% of individuals aged over 55 have chronic knee pain, often due to osteoarthritis. Knee pain originates from the joint due to structural changes or inflammation (peripheral mechanisms), and is often intensified by processing of afferent signals within the central nervous system (central mechanisms). We aimed to investigate whether baseline measures associated with central sensitization, including a simple self-report ‘central mechanism’ trait score and Pressure Pain Detection Thresholds (PPTs), predict future pain outcomes in individuals with knee pain.

Methods: Data from participants consenting to the Knee Pain In the Community (KPIC) study were analysed. 1,471 participants reported knee pain at baseline and responded to a 1-year follow-up questionnaire. Of these, 204 participants underwent further radiographic and PPT assessments at baseline. A summary score for a latent self-report ‘central mechanisms’ trait was derived from baseline scores for 8 questionnaire items, representing component traits of anxiety, depression, catastrophizing, neuropathic-like pain, fatigue, sleep disturbance, pain distribution, or cognitive impact. Presence/absence of pain persistence (pain present at baseline and year 1) served as the primary pain outcome. In those reporting pain persistence, persistent pain severity (residualized pain severity change scores) served as the secondary pain outcome. Prediction of pain outcomes by baseline scores for the central mechanisms trait and PPTs used logistic and linear regression models. Receiver-operator-characteristic (ROC) curves and areas-under-the-curve (AUC) compared the predictive strength of the central mechanisms trait to other predictors of pain persistence.

Results: 976 (66%) individuals reported pain persistence, of whom 118 individuals underwent further assessments at baseline. The central mechanisms trait score was a significant predictor for pain outcomes (pain persistence: Relative Risk, RR = 1.73, n = 1471, p < 0.001; Persistent pain severity: β = 0.47, n = 976, p < 0.001), even after adjustment for age, sex, BMI, radiographic OA and symptom duration (pain persistence: RR = 2.14, n = 204, p = 0.001; persistent pain severity: β = 0.47, n = 118; p < 0.002). Lower medial joint-line PPT was associated with persistent pain severity (β=-0.32, n = 118, p = 0.007). The central mechanisms trait score model showed good discrimination power in distinguishing pain persistence cases from resolved pain cases (AUC = 0.70; n = 1471). The discrimination power of other predictors, including radiographic OA (AUC = 0.62; n = 204), age, sex and BMI (AUC range = 0.51 to 0.64; n = 1471), improved significantly (p < 0.04) when the central mechanisms trait was included in each univariate logistic regression model (AUC range = 0.69 to 0.74).

Conclusion: A simple self-report ‘central mechanisms’ trait score, consisting of 8 self-report items, shows prognostic value in identifying individuals more likely to report knee pain persistence at follow-up. This might indicate a contribution of central mechanisms to poor knee pain prognosis. Ongoing work seeks to validate a newly developed questionnaire based on these 8 items for use in clinical practice and epidemiological research settings.

Disclosures: K. Akin-Akinyosoye: None. N. Frowd: None. L. Swaithes: None. J. Stocks: None. A. Sarmanova: None. G. Fernandes: None. A. Valdes: None. D.F. McWilliams: None. W. Zhang: Consultancies; AstraZeneca (Lesinurad), and Gruenthal (Lesinurad). Member of speakers’ bureau; Husin (Chinese Society of Rheumatology Annual Congress 2016), Bioberica (EULAR 2016 symposium). M. Doherty: None. E. Ferguson: Corporate appointments; Deputy Editor British Journal of Psychology, Associate Editor for Annals of Behavioral Medicine. Royalties; GL assessment for the Paediatric Index of Emotional Distress (PI-ED). Honoraria; Invited speaker at ISBT (expenses and travel paid). Grants/research support; Co-investigator on a grant from the US Defense Medical Research and Development Program (Study to examine psychological processes in suicidal ideation and behaviour)., Co-investigator on a grant from the ESRC (Individual Differences in the Impact of Socio- Economic Events on Health and Well-being)., Co-investigator on a grant from the ESRC (Integrating Prospect theory (Framing Effects) and the Common Sense Model of illness to improve medication compliance in glaucoma patients), Co-investigator on a grant from Chief Scientists Office – Scotland (A randomised controlled trial to test if a simple anticipated regret manipulation leads to an increase in organ donor registration, Co-investigator on a grant from DEFRA (Overcoming barriers to uptake of best welfare practice by sheep farmers), Co-investigator on a grant from Pfizer (Pain phenotypes in rheumatoid arthritis, Co-investigator on a grant from Arthritis UK Research (Pain Centre) that funds the current work. D. Walsh: Corporate appointments; University of Nottingham as Professor of Rheumatology, Director of Arthritis Research UK Pain Centre, Musculoskeletal Theme lead in the NIHR Nottingham Biomedical Research Centre, Honorary consultant appointments with Sherwood Forest Hospitals NHS Foundation Trust and Nottingham University Hospitals NHS Trust. Consultancies; Consultancy for Pfizer Ltd 2017 undertaken through Nottingham University Consultancy Ltd, providing approximately £3,000 to facilitate staff development within the Arthritis Research UK Pain Centre. Grants/research support; Co applicant: Nottingham Hospital Charity N of 1 trial for topical ibuprofen gel and capsaicin cream, NIHR Clinical Research Facility of £2.4 across 5 research themes in Nottingham, NIHR Biomedical Research Centre (musculoskeletal theme) of £23.6m total award to Nottingham., ERAN Database support, Arthritis Research Campaign Centre Initiative grant Centre of Excellence in Mechanisms of Pain in Arthritis. Other; Trustee of the Early Rheumatoid Arthritis Network, UK Registered Charity.