A study estimated the lifetime risk of symptomatic knee osteoarthritis (OA) in a longitudinal study of 3,068 participants in Johnston County, North Carolina, aged ≥45 years. The lifetime risk of developing symptomatic knee OA was found to be 44.7% (95% CI 40.0–49.3%). This risk increased with higher body mass index (BMI), with a 2 in 3 risk among obese individuals. Participants with a history of knee injury had a higher risk (56.8% vs. 42.3%). The study also found that the risk was higher among women, blacks, and those with lower education levels. The results suggest that nearly half of the adults in Johnston County will develop symptomatic knee OA by age 85, with the highest risk among obese individuals. These findings indicate that similar high risks may exist in the general US population, especially given the increasing prevalence of obesity and aging. The study emphasizes the need for public health interventions, particularly those addressing weight loss and self-management, to reduce the impact of knee OA. The study used logistic regression models with generalized estimating equations to estimate lifetime risk, accounting for repeated measures and correlated data. The study also considered the impact of missing data and attrition in longitudinal studies. The results highlight the importance of understanding and addressing the risk factors for knee OA to reduce its public health burden.A study estimated the lifetime risk of symptomatic knee osteoarthritis (OA) in a longitudinal study of 3,068 participants in Johnston County, North Carolina, aged ≥45 years. The lifetime risk of developing symptomatic knee OA was found to be 44.7% (95% CI 40.0–49.3%). This risk increased with higher body mass index (BMI), with a 2 in 3 risk among obese individuals. Participants with a history of knee injury had a higher risk (56.8% vs. 42.3%). The study also found that the risk was higher among women, blacks, and those with lower education levels. The results suggest that nearly half of the adults in Johnston County will develop symptomatic knee OA by age 85, with the highest risk among obese individuals. These findings indicate that similar high risks may exist in the general US population, especially given the increasing prevalence of obesity and aging. The study emphasizes the need for public health interventions, particularly those addressing weight loss and self-management, to reduce the impact of knee OA. The study used logistic regression models with generalized estimating equations to estimate lifetime risk, accounting for repeated measures and correlated data. The study also considered the impact of missing data and attrition in longitudinal studies. The results highlight the importance of understanding and addressing the risk factors for knee OA to reduce its public health burden.