Keele Research Repository

OBJECTIVE: Osteoarthritis (OA) is a heterogeneous disease with symptom progression at the foot unclear. This study investigated the symptomatic course of three pre-defined foot OA phenotypes over an 18-month period. METHODS: The Clinical Assessment Study of the Foot (CASF) is a community-based cohort of adults aged ≥50 years in North Staffordshire, UK. Participants who reported foot pain in a postal health survey and underwent radiographic assessment were mailed an 18-month follow-up survey. Changes in descriptive and symptomatic outcomes over 18 months were compared across the three phenotypes to determine within-phenotype changes and between-phenotype differences. RESULTS: Of 533 participants at baseline, 478 (89.7%) responded at 18 months. All three phenotypes showed small within-phenotype improvements in mean foot pain severity (scale from 0=no pain to 10=worst pain): no or minimal foot OA (18-month 4.0; mean change -1.15 [95% CI -1.46,-0.83]), isolated first metatarsophalangeal joint (MTPJ) OA (18-month 4.1; mean change -0.60 [95% CI -1.11,-0.10]) and polyarticular foot OA (18-month 5.1; mean change -0.77 [95% CI -1.42,-0.12]). The isolated first MTPJ OA phenotype had an increased likelihood of hallux valgus in the left foot (adjusted odds ratio 2.96 [95% CI 1.23,7.12]) compared to the no or minimal foot OA phenotype. CONCLUSION: Three foot OA phenotypes showed few descriptive or symptomatic changes over 18 months. Future clinical trials should consider that people recruited with mild-to-moderate symptomatic foot OA appear likely to remain relatively stable with usual care. Longer-term follow-up using additional time-points is required to describe further the natural history of foot OA. This article is protected by copyright. All rights reserved.