Aim: To assess the serum Vitamin D levels and Kellgren-Lawrence grading in patients of Primary Osteoarthritis. Materials and Methods: The present observational study was carried out on the patients coming to the OPD of the Department of Orthopedics, SMS Medical College and Hospital, Jaipur. All patients complaining of Osteoarthritis of the knee joint and willing to participate in the study were interviewed for age, sex, history of inflammatory arthritis or any rheumatic disease, complain of celiac disease & malabsorption syndrome or any history of intake of any drug that might affect serum Vit D levels. After the successful running of Quality Controls the clear serum obtained from patient’s serum was analyzed on Advia Centaur XP (for Vitamin D & PTH) & fully automated chemistry analyzer Beckman Coulter AU 680 (for routine biochemical parameters). Based on the serum biochemistry results, patients with deranged RFT & LFT were excluded from the study & the Serum Vitamin D, PTH, Calcium and Phosphorus levels of the patients with normal RFT & LFT were documented.