A prospective randomized clinical trial was conducted on 162 patients of osteoarthritis of knee were included in the study. The patients were divided into two groups- Group A and Group B. The Group A was treated with shortwave diathermy, exercise, naproxen and activity modification and the Group B was treated with shortwave diathermy, exercise and naproxen. Improvement was found more in Group A than Group B after 4th week (95 % CI was -2.59 to 6.56). Then it was found that the improvement was gradually increased in Group A than Group B and finally, it was found that there was highly significant improvement in Group A than Group B after 6th week (95 % CI was -3.45 to -0.70). This study suggests that activity modification play an important role for the treatment of the patients with osteoarthritis of knee.