Background: The purpose of this study was to find out the real truth of the effect of PROM (Passive range of motion) and AAROM (Active assistive range of motion) exercise on increasing the knee flexion. This randomized, controlled trial examined whether or not the incorporation of PROME(passive range of motion exercise) to a postoperative rehabilitation protocol would offer a better clinical outcome after TKA (Total knee arthroplasty) Method: The subject (n=36) measured range of motion (ROM).18 consecutive patients who underwent TKAs at SNUH dept. OS received PROME for knee by a physical therapist during the physiotherapy sessions and not for the other 18 patients who underwent TKAs received No-PROME (AAROME) for knee by herself. Result: There were significant differences in the PROME group, No-PROME group ROM progress width And there were significant differences in the PROME group between No-PROME group ROM improvement width. Conclusion: This study demonstrates that the incorporation of PROME does offer additional clinical benefits to the patients after TKA. Our findings may suggest that encouraging patients to perform PROM exercises would be a better option and that physiotherapy session by a physical therapist holds good even now.