BACKGROUND: Knee osteoarthritis (KOA) is a major global health challenge, with rising prevalence, incidence, and disability-adjusted life years (DALYs). This disease increasingly burdens healthcare systems worldwide, particularly as populations age and obesity rates rise. In China, the rapid demographic shift towards an aging population, combined with rising obesity rates, makes KOA a pressing public health issue. China is projected to experience a significant increase in the number of elderly individuals, who are particularly vulnerable to KOA. Additionally, gender disparities, with women being more affected, add further urgency. Addressing KOA in China requires targeted healthcare strategies, considering these unique demographic and lifestyle factors. METHODS: We utilized data from the Global Burden of Disease (GBD) 2021 database to assess the prevalence, incidence, and DALYs related to KOA both globally and in China. The decomposition analysis was used to evaluate the contributions of population aging, growth, and epidemiological changes. For prediction, we employed the Bayesian Age-Period-Cohort (BAPC) model, implemented using the Integrated Nested Laplace Approximation (INLA) method, to project future trends from 2022 to 2045. RESULTS: From 1990 to 2021, both China and globally experienced significant increases in the burden of KOA. In China, the age-standardized prevalence rate (ASPR) increased from 4,667.29 (95% UI: 3,996.06-5,359.85) per 100,000 in 1990 to 5,016.52 (95% UI: 4,265.22-5,758.38) per 100,000 in 2021. Globally, the ASPR rose from 3,964.75 (95% UI: 3,411.86-4,536.4) per 100,000 in 1990 to 4,294.27 (95% UI: 3,695.04-4,910.76) per 100,000 in 2021. Similarly, the age-standardized incidence rate (ASIR) in China increased from 377.93 (95% UI: 324.79-434.28) per 100,000 in 1990 to 406.42 (95% UI: 348.7-467.23) per 100,000 in 2021, compared to a global increase from 330.26 (95% UI: 284.34-375.75) to 353.67 (95% UI: 304.56-402.5). The age-standardized DALY rate (ASDR) in China rose from 151.24 (95% UI: 72.96-291.47) per 100,000 in 1990 to 162.44 (95% UI: 78.35-314.13) per 100,000 in 2021, whereas the global ASDR rose from 127.14 (95% UI: 62.17-246.99) per 100,000 in 1990 to 137.59 (95% UI: 67.08-266.87) per 100,000 in 2021. The prevalence, incidence, and DALYs of KOA were consistently higher in females compared to males. In both regions, population growth had the most significant impact on KOA burden, but population aging was a more significant factor in China. High BMI and metabolic risk factors, particularly in females, were identified as key contributors to KOA-related DALYs. This study projects the trends in knee osteoarthritis (KOA) burden in China and globally by 2045. In China, the Age-Standardized Prevalence Rate (ASPR) is projected to increase by approximately 2.5% (from 5016.52 to 5142.90), while the Age-Standardized Incidence Rate (ASIR) is expected to decrease by about 8.8% (from 406.43 to 370.72). Globally, the ASPR is expected to rise by around 7.8% (from 4294.26 to 4630.97), while the ASIR is projected to increase by 5.8% (from 353.67 to 374.13). The Age-Standardized Death Rate (ASDR) is expected to increase in both China (by 1.3%, from 162.44 to 164.61) and globally (by 5.7%, from 137.59 to 145.45). These projections suggest an overall rise in the burden of KOA, with regional variations. CONCLUSION: KOA remains a significant and increasingly complex global health challenge, with its burden expected to rise sharply in the coming decades. This study highlights that in both China and globally, the escalating prevalence of KOA is closely linked to population aging and obesity, but the drivers vary across regions. In China, the rising burden is predominantly influenced by demographic aging, making it critical to develop targeted interventions that address the needs of an aging population. Globally, the expansion of the population is the primary contributor to the increased KOA burden, which underscores the importance of integrating KOA prevention into broader public health strategies aimed at managing population growth and associated lifestyle risks. The findings underscore the urgency of addressing obesity as a key risk factor for KOA, especially in women. Public health interventions should focus on obesity prevention, particularly in middle-aged and older populations, and include strategies such as promoting healthier diets, physical activity, and metabolic health management. Furthermore, policies aimed at improving joint health in aging populations, with a focus on early diagnosis and rehabilitation, could significantly alleviate the long-term societal and healthcare costs associated with KOA.