Pain Trajectories and Mechanisms in Early Inflammatory Arthritis: Results from a 2-Year Prospective Cohort

Abstract Introduction Pain is often persistent in patients with inflammatory arthritis (IA). There is limited research on pain mechanisms in early IA. We used detailed assessments to characterise pain types longitudinally. Methods This prospective observational study investigated the relative contribution of peripheral versus centrally mediated pain in newly diagnosed IA patients with pain scores ≥3, followed over two years. Assessments included: disease activity (Disease Activity Score-28, musculoskeletal ultrasound); quality of life (Musculoskeletal Health questionnaire); mental health status (Patient Health Questionnaire Anxiety, Depression Scale) and pain characteristics (Fibromyalgia criteria, painDETECT, Static and Dynamic Quantitative Sensory Testing). Mixed-effects regression models examined longitudinal associations. Results Among 66 participants (all baseline pain NRS ≥3), pain decreased significantly in the first six months, with smaller, non-significant reductions thereafter. At 24 months, 49% still reported pain (NRS ≥3) and 25% showed no pain improvement. Those with pain had higher baseline and longitudinal scores for centrally mediated pain (fibromyalgia severity, painDETECT) and psychological distress, despite similar baseline inflammation and similar reductions over time. Both baseline and longitudinal inflammation was not associated with subsequent pain ( b –0.05, 95% CI –0.67 to 0.56), whereas higher centrally mediated pain markers predicted less pain reduction ( b 1.41, 95% CI 0.83–1.99, p