Clinical evaluation of usefulness and effectiveness of sitting-type continuous passive motion machines in patients with total knee arthroplasty: a dual-center randomized controlled trial

Background: Total knee arthroplasty (TKA) is a treatment option for osteoarthritis of the knee. After undergoing TKA, patients can be treated with continuous passive motion (CPM); however, inconsistent results have been reported on the effectiveness of CPM as part of a rehabilitation strategy. This discrepancy may be due to the difference between the set-arc of CPM and real arcs of knee motion. In this randomized controlled trial, we compared the efficacy of the sitting-type CPM, which can apply a more fitted arc of motion, to that of the conventional CPM. Methods: We performed a prospective, multicenter, single-blind, three-arm, randomized controlled trial. Patients who underwent unilateral TKA were recruited and randomly allocated to three groups (151 participants; Group 1, conventional type; Group 2, mixed; and Group 3, sitting type). All participants underwent 10 days of CPM management. Passive and active ranges of motion (ROMs), pain, lower-extremity edema, patient-reported outcomes, and functional assessments were evaluated at four time points. Results: Passive and active ROMs and pain significantly improved during and after the intervention in all groups; however, no significant differences were noted between the groups. Compared with the conventional type, the sitting-type CPM devices were rated higher in participant’s satisfaction questionnaires. Conclusion: The sitting-type CPM had equivalent efficacy to that of the conventional-type CPM but provided higher satisfaction to patients after TKA. Therefore, the sitting-type CPM may be a useful tool in post-TKA rehabilitation. Clinical trial registration: This clincial trial was registed with the Clinical Research Information Service of Republic of Korea, KCT0005520, Registered on 21 October 2020, date of first enrollment at 10/11/2020 https://cris.nih.go.kr/cris/search/detailSearch.do/21750.