Natural history of pain and disability among African–Americans and Whites with or at risk for knee osteoarthritis: A longitudinal study

Objective: Compare knee pain and disability between African Americans (AAs) and Whites (WHs), with or at risk of knee osteoarthritis (KOA), over 9 years, and evaluate racial disparities in KOA-related symptoms across socioeconomic and clinical characteristics. Design: Osteoarthritis Initiative (OAI) participants were evaluated annually over 9 years for pain and disability, assessed by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and a numerical rating scale (NRS) for knee pain severity. Mean annual WOMAC pain, NRS pain, and WOMAC disability levels were estimated by race using mixed effects models, adjusted for age, sex, education, marital status, body mass index (BMI), depression, and baseline Kellgren–Lawrence grade score. Race-specific mean WOMAC pain scores were also estimated in analyses stratified by socioeconomic and clinical characteristics. Results: AAs reported worse mean WOMAC pain compared to WHs at baseline (3.69 vs 2.20; P ≤ 0.0001) and over 9 years of follow-up, with similar disparities reflected in NRS pain severity and WOMAC disability. Radiographic severity did not account for the differences in pain and disability, as substantial and significant racial disparities were observed after stratification by Kellgren–Lawrence grade. Depression and low income exacerbated differences in WOMAC pain between AAs and WHs by a substantial and significant magnitude. Conclusions: Over 9 years of follow-up, AAs reported persistently greater KOA symptoms than WHs. Socioeconomically and clinically disadvantaged AAs reported the most pronounced disparities in pain and disability.