Study Comparing GAP-Flex to CPM Therapy in Treatment of TKR

Inclusion Criteria: * Minimum age 50 years * Subject is undergoing total knee replacement * Subject agrees to comply with the physical therapy regime Exclusion Criteria: * With a flexure contracture \> 10 degrees * Degree of flexion \< 60 degrees pre-procedure or immediately post-procedure * Severe motion restriction as determined by the investigator * Severe deformity determined by the investigator * Taking chronic pain medication for use other than knee pain * Post surgery hospital stay is \> 4 days * Knee disorders other than osteoarthritis * With fibromyalgia * Chronic narcotic use as determined by the investigator. * Have a medical or psychological history that in the opinion of the investigator would make the subject a poor candidate for the study. * Who need a revision implant * Who have participated in clinical study within the past 30 days (prior to enrollment) that may affect the outcome of this study * Amputations below or above knee of non-operated leg * Weight is \>250 pounds and/or morbidly obese (BMI \> 40) * History of blood clots * Deep vein thrombosis * Females who are pregnant * Females who wish to become pregnant during the length of study participation * Subjects with any of the following post-surgery conditions; * Screws needed * Intraoperative identification of a fracture or soft bone * Admitted to ICU * Additional procedures (other than TKR) needed for other identified or pre-existing conditions