Abstract : Osteoarthritis of the knee is a common chronic disorder having a significant morbidity. Etiopathogenesis of OA is multifactorial. Muscle imbalance is one of the causes of OA knee. Quadriceps muscle weakness is one of the significant predictors is progress of OA. Hence quadriceps muscle strengthening is one of the strongly recommended treatment modalities. Studies have shown that VMO is more selectively affected among the quadriceps muscles. This study is conducted to assess the effect of addition of VMO specific strengthening exercises to quadriceps exercises in the treatment of KL Grade I- III OA knee. 60 subjects with primary OA were randomized into two groups VMO + Quads and VMO alone. Allocation concealment and blinding was done. Subjects were taught exercises daily for one week, and weekly for the next 3 weeks. VAS and WOMAC scores were recorded at the baseline and at 1,3,6 and 12 months. Both groups were comparable at the baseline. Both groups showed a significant improvement in VAS and WOMAC scores at 1 year follow -up compared to the baseline. When inter group comparisons were made, there was no difference in pain scores in any of the follow up. However VMO + quads group showed a significant improvement in WOMAC scores at 1 and 3 months follow up which evened out at the 6 and 12 months follow up. Quadriceps exercises and the addition of VMO exercises to the quads group showed significant improvement in pain and functional outcomes in OA knee. The addition of VMO also shows a significant improvement in functional outcomes at 1 and 3 months of follow up.