Purpose: This study was to investigate the effect of isometric exercise and active stretching on joint function in patient with osteoarthritis. Methods: 30(M=1, F=29) subjects with osteoarthritis were divided in three groups: control group, quadriceps isometric exercise group, and hamstring active stretching group. After 6 weeks treatment, ROM(range of motion) and LSS(lysholm scoring scale) were measured. Results: There was a significant increase in knee flexion, extension in post-treat of quadriceps isometric exercise group and hamstring active stretching group(p<0.05). There was a significant increase in LSS in post-treat of quadriceps isometric exercise group and hamstring active stretching group(p<0.05). Conclusion: This study shows that both the active stretching exercise and the quadriceps isometric exercise effectively promote the range of knee extensions for osteoarthritis patients. Also, as measuring the ROM of knee flexion and extension by exercise methods, there is significant increase from knee flexion and extension in both hamstring stretching exercise group and quadriceps isometric exercise group. The increase of the range of knee is more effective in the exercise of knee extension with hamstring stretching exercise groups. And it is found that there are some difference between the experimental group and controlled group in statistics. As it is concerned with the function of knee extension, supporting and squatting are more effective to promote the both knee extension and flexion in its range. Therefore, this shows that the hamstring stretching exercise is required in general with enforcing the quadriceps at a sickbed in the present.