The effects of two different continuous passive motion protocols on knee range of motion after total knee arthroplasty: a prospective analysis

Abstract

We prospectively evaluated the effects of continuous passive motion (CPM) started after two different time intervals following total knee arthroplasty (TKA) on short- and long-term results, in comparison with standard physical therapy. Eighty-six patients were randomized to three groups following TKA for primary osteoarthritis. The control group (n=28) received only conventional physical therapy. Group I and II, each consisting of 29 patients, were treated with conventional physical therapy combined with CPM that was started on the first and third postoperative days, respectively, and continued until discharge with three one-hour sessions daily. Preoperative and postoperative measurements of the knee range of motion were recorded. Clinical and functional results were assessed using the Knee Society rating system. The patients were followed-up for at least two years (range 26 to 52 months). The duration of CPM was 22 hours in group I, and 19 hours in group II (p>0.05). Knee flexion values measured in the CPM groups on day 3 and at discharge showed significant differences with those of the control group, but no significant differences were found between the groups after the first postoperative month in this respect (p>0.05). The mean duration to reach 100 degrees of passive knee flexion (p=0.03) and the mean length of hospital stay (p=0.04) in the CPM groups were shorter by three and two days compared to the control group, respectively. Clinical and functional knee scores showed significant improvements in all the groups postoperatively (p<0.001), but there were no significant differences between the groups with respect to pre-and postoperative knee scores (p>0.05). Even though CPM protocols applied following TKA may shorten the length of hospital stay, CPM applications do not offer additional short- and long-term benefits over standard physical therapy with respect to knee flexion and clinical and functional results.