OBJECTIVE: To investigate the risk factors for symptomatic knee osteoarthritis (OA) in Koreans METHODS: A total of 1,194 persons consisting of 588 men and 606 women (mean age+/-SD, 48.9+/-14.0 years) were enrolled in rural and urban areas or in a hospital of Korea between september 2000 and august 2001. All participants were interviewed about symptoms of knee OA and possible risk factors including age, sex, occupation, body mass index (BMI), smoking, age of menarche, menopause and hormone replacement therapy and examined. Knee radiograph was obtained in all participants with knee symptoms. Symptomatic knee OA was defined according to clinical criteria or clinical and radiographic criteria for classification of osteoarthritis of the knee by Altman. RESULTS: Of 1,194 participants, symptomatic knee OA was found in 189 persons (15.8%) and multivariate analysis showed that female (OR=5.66, 95% CI 3.42~9.38), aging (OR=1.10, 95% CI 1.08~1.12), living in rural area (OR=3.83, 95% CI 2.27~6.45) and BMI over 25 kg/m(2) (OR=2.26, 95% CI 1.42~3.59) were risk factors. Age (older than 70 years, OR=1.08, 95% CI 1.04~1.12) and living in rural area (OR=5.39, 05% CI 1.94~14.96) were associated with symptomatic knee OA in men and age (older than 40 years, OR=1.11, 95% CI 1.07~1.16), living in rural area (OR=2.46, 95% CI 1.17~5.17), and BMI over 25 kg/m(2) (OR=3.45, 95% CI 1.63~7.29) in women. CONCLUSION: The risk factors for symptomatic knee OA were aging, female, living in rural area and high BMI in Koreans.