Introduction: Osteoarthritis of knee is a widespread, slowly developing disease with a high prevalence with age, with greater body weight and in post menopausal women. The main causes of functional dysfunction in osteoarthritic knee are pain and quadriceps muscle weakness. Physical rehabilitation usually includes quadriceps exercises i.e. isometric and isotonic exercises for the maintenance of joint range of motion and muscle strength. Biofeedback is a process that can be combined with it to increase the awareness about the extent of muscle work done by quadriceps muscle. The aim of the study was to compare the effectiveness of different quadriceps strengthening protocols with or without biofeedback in improvement of extensor lag in osteoarthritic knee joint. Materials & Methods: Sixty osteoarthritic knee patients with twenty patients each in three groups were randomly selected from Guru Harkrishan Hospital, Sarai Kale khan and Physical rehabilitation clinics in Delhi. Patients were randomly divided into three groups A, B and C. Research Design was Experimental study. Dependent Variables were Quardiceps Lag and Knee ROM .Independent Variables were Biofeedback and Modified Quadriceps Exercise which were introduced to the subjects. ANOVA test was applied to find out the statistical level of significance. Results: There was a great improvement of extensor lag in group C who had received Modified Quadriceps Sets with Biofeedback when compared with group B and group A. The percentage of reduction in pain was more and ROM was more increased in group C when compared with group B and A. Discussion & Conclusion: Modified quadriceps sets with biofeedback are better than the quadriceps sets and quadriceps sets with biofeedback in improvement of extensor lag in osteoarthric knee patients.