Identifying long-term trajectories of foot pain severity and potential prognostic factors: a population-based cohort study

Objectives To identify distinct foot pain trajectories over seven years and examine their associations with potential prognostic factors. Methods Adults aged ≥50 years registered with four general practices in North Staffordshire, UK were mailed a baseline health survey. Those reporting current or recent foot pain were invited to attend a research assessment clinic. Follow-up was by repeated postal surveys at 18, 36, 54, and 84 months. Distinct trajectories of foot pain were explored using Latent Class Growth Analysis (LCGA). Subsequently, identified trajectories were combined into most and least progressive groups and covariate-adjusted associations with a range of prognostic factors examined. Results Of 560 adults with foot pain attending baseline research clinics, 425 (76%) provided data at baseline and ≥2 follow-up time-points. LCGA for foot pain severity (0-10 Numerical Rating Scale) identified a four-trajectory model: 'mild, improving' (37%); 'moderate, improving' (33%); 'moderate-severe, persistent; (24%); 'severe, persistent' (6%). Compared with individuals in more favourable ('improving') pain trajectories, those in less favourable ('persistent') pain trajectories were more likely to be obese, have routine/manual and intermediate occupations, poorer physical and mental health, catastrophising beliefs, greater foot-specific functional limitation, and self-assessed hallux valgus at baseline. Conclusions Four distinct trajectories of foot pain were identified over a seven-year period, with one-third of individuals classified as having pain that is persistently moderate-severe and severe in intensity. The effect of intervening to target modifiable prognostic factors such as obesity and hallux valgus on long-term outcomes in people with foot pain requires investigation.