This study investigated the epidemiology (prevalence, risk factors, and impact on quality of life) of knee pain and its severity in elderly Koreans. The subjects (n=3,054) were participants aged ≥50 yr from the fifth Korea National Health and Nutrition Examination Survey, conducted in 2010. Knee pain was defined as pain in the knee lasting ≥30 days during the most recent 3 months; severity was categorized as mild, moderate, or severe. EQ-5D was used to measure quality of life. The prevalence of knee pain was 23.1% (11.7% in men, 31.9% in women). The prevalences of mild, moderate, and severe knee pain were 4.3%, 9.1%, and 9.7%, respectively (2.8%, 5.4%, and 3.5% in men and 5.4%, 12.0%, and 14.4% in women). Old age, female gender, a low level of education, a manual occupation, obesity, and radiographic osteoarthritis were risk factors for knee pain, and were associated with increased severity of knee pain. Excluding men with mild knee pain, people with knee pain had significantly lower quality of life than those without knee pain. Early interventional approaches are needed to reduce the medical, social, and economic burden of knee pain in elderly Koreans.