Abstract
BACKGROUND: Knee osteoarthritis (KOA) is a major global cause of disability. Traditional burden metrics quantify disease magnitude but may overlook system-level outcomes. The Chronic Disease Quality of Life Index (CD-QoLI) was developed to capture these broader impacts. OBJECTIVES: To assess the global impact of KOA using the CD-QoLI, focusing on long-term trends, regional disparities, and future projections. DESIGN: A global population-based modelling study. METHODS: KOA data were obtained from the Global Burden of Disease Study and included incidence, prevalence, and years lived with disability (YLDs) across 204 countries and territories. CD-QoLI was derived from two standardized epidemiological ratios to reflect system-level outcomes. Temporal trends were quantified using annual average percentage change (AAPC), and forecasting models projected values to 2040. Analyses were stratified by sex, age, and Sociodemographic Index (SDI) regions. RESULTS: Globally, KOA incidence, prevalence, and YLDs increased substantially over the study period. Over the same period, CD-QoLI declined from 0.812 to 0.700 (AAPC: -0.50); in this study, lower CD-QoLI values indicate a relatively more favorable system-level balance between KOA burden and outcomes, and declines were more pronounced in high- and middle-SDI regions. Females and older adults consistently showed lower scores, while individuals aged 15-49 years exhibited a reversal from decline to improvement after 2014. Low-SDI regions displayed persistently higher or rising CD-QoLI values. Spatial analyses indicated marked cross-national heterogeneity, with several high-income countries showing increasing CD-QoLI trajectories over time, whereas others experienced notable declines. Overall, CD-QoLI levels were strongly inversely correlated with SDI (ρ = -0.884). Projections to 2040 indicate persistent disparities, particularly among younger populations and low-SDI areas. CONCLUSION: Although KOA burden continues to rise, improvements in system-level outcomes remain uneven across regions, age groups, and development levels, emphasizing the need for targeted and equitable chronic care strategies.