BACKGROUND AND OBJECTIVE Nutritional imbalance, combined with endocrine abnormalities, may be involved in the pathogenesis of osteoarthritis (OA). This study was conducted to determine the association of OA with dietary factors, such as quantity and quality of nutrient intake. METHODS This case-control study enrolled 180 knee osteoarthritis (KOA) subjects who met the American College of Rheumatology definition of KOA, with an equal number of matched controls. Outcome measures, such as dietary nutrient intake and its frequency, were recorded using a food frequency questionnaire. RESULTS Compared to controls, cases were older individuals with a higher body mass index (BMI). Physical activity scores were lower in female cases compared to male cases and controls. A significantly higher intake of phosphorus and fat was observed in overall cases (fat in females only). A significantly lower intake of vitamin C and vitamin D was observed in overall cases and the significance of vitamin D persisted on gender-wise bifurcation. On multiple logistic regression analysis, the intake of vitamin D (odds ratio [OR] = 0.79) and vitamin C (OR = 0.97) was inversely associated with the presence of KOA in the observation group, especially in females. Generally, the intake of food servings/day, green leafy vegetables (GLVs), and fats/oils was higher, whereas the intake of fruits, milk/milk products, and meat/poultry was lower in cases compared to controls. CONCLUSION Low intake of vitamin D and vitamin C is a possible risk factor for KOA. Certain food groups, such as fruits, milk/milk products, and meat/poultry are beneficial for KOA. Further studies are needed to elucidate the associations between diet and KOA.