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

Abstract 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 .