Background: Arthritis is inflammation of joints which leads to pain and stiffness that worsens with age. Patellofemoral arthritis affects the underside of the patella and the channel-like groove in the femur that the patella rests in. PFPS is an overuse injury in which anterior knee pain is present. The patient with patellofemoral arthritis has kneecap pain, stiffness and often swelling in the front part of the knee that typically worsens when walking on inclined terrain, climbing stairs, squatting. The patients with patellofemoral arthritis have reduced functional ability due to pain. It is important to increase the strength of Vastus Medialis Oblique Muscle which helps in stabilizing the patella during knee joint movements in order to reduce the pain. Aquatic physical therapy is considered as a safe and effective treatment program for managing knee OA as it contribute to the increase in the pain threshold and it also decreases the joint overload and pain symptoms and improves functionality and quality of life. Objective: To compare the effect of aquatic therapy and Vastus Medialis Oblique strengthening on pain and functional ability in patellofemoral arthritis (PFA). Materials and methods: An experimental study was conducted on total of 30 subjects on the basis of inclusion and exclusion criteria with 15 subjects in group A for VMO strengthening and 15 subjects in group B for aquatic therapy exercise. Outcome measures used were Visual Analogue Scale (VAS) and Anterior Knee Pain Scale (AKPS). The protocol was conducted for 5 weeks, 3 days a week. Results: A total of 30 patients between the age of 40-65 years were included. Statistically it shows that there was extremely significant difference (p<0.0001) between pre intervention assessment and post intervention assessment. But the subjects treated with aquatic therapy shows more significant difference than the subjects treated with VMO strengthening program. Conclusion: The present study concludes that the aquatic therapy program is more effective than the VMO strengthening program which showed more reduction in pain and increase in functional ability in PFA. KEY WORDS: Patellofemoral arthritis, Patellofemoral pain syndrome, knee pain, VMO strengthening, Aquatic therapy, Visual Analogue Scale, Anterior Knee Pain Scale.