This study aimed to determine the effects of using a continuous passive motion (CPM) device for patients with poor range of motion (ROM) after a total knee replacement (TKR) admitted for postacute rehabilitation. Adults (N=141) after TKR with initial active knee flexion <75° on admission to the IRF participated in the study. Two randomized groups: group 1 (n=71) were given the conventional 3 hours of therapy per day, and group 2 (n=70) received the addition of daily CPM use for 2 hours throughout their length of stay. The primary outcome measure was active knee flexion ROM. Secondary outcome measures included active knee extension ROM length of stay, estimate of function using the FIM and Timed Up and Go test, girth measurement, and self-reported Western Ontario and McMaster Universities Osteoarthritis Index scores. All participants significantly improved from admission to discharge in all outcome measures. However, there weren't any statistically significant differences in any of the discharge outcome measures of the CPM group compared with the non-CPM group.
The study did not find CPM to provide an additional benefit over the conventional interventions used in an IRF for patient after TKR, specifically in patients with poor initial knee flexion ROM after surgery.