We compared the effects of continuous passive motion (CPM) given for a minimum of 20 hours a day to Group 1 patients (n = 15) or a maximum of 5 hours a day to Group 2 patients (n = 8) who received total knee joint replacements. Four variables were analyzed on the third and sixth days after surgery: 1) range of motion, 2) edema-effusion, 3) pain, and 4) length of hospital stay. We found significant improvements in knee extension (p less [corrected] than .001) in the Group 2 patients on Day 6 after surgery. We also found a significant negative correlation between the length of hospital stay and the number of physical therapy treatments received. No between-group differences were found in measurements of 1) total knee excursion, 2) edema-effusion, 3) pain, 4) length of hospital stay, and 5) number of PT treatments received. This lack of differences implies that comparable results can be obtained by using the CPM machine either 20 hours a day or 5 hours a day.