Continuous Passive Motion (CPM)
Introduction[edit | edit source]
Continuous Passive Motion (CPM) therapy uses machines to move a joint passively i.e. without the patient exerting any effort. A motorised device moves the joint repetitively to a set of number of degrees and movement speed, determined by the physiotherapist. CPM machines are most commonly applied to the knee, but there are versions for other joints such as the hip, shoulder and elbow.
Uses of CPM[edit | edit source]
CPM is most commonly used after joint surgery to promote the recovery of normal joint range of motion (ROM) and thus, to prevent joint stiffness complications. It is frequently recommended after knee joint replacement or knee cartilage repair surgery. Uses of the CPM are also reported in pediatric orthopaedic surgeries or injuries for maintaining hip and knee range of motion. CPM was introduced in the early post-operative period and was combined with physiotherapy for maximum results. The device was well tolerated, without interfering with open wounds, nursing care or external fixation devices. 
Mechanisms of action, timing and effectiveness[edit | edit source]
Joint stiffness after surgery or injury is reported to progress through four stages: bleeding, edema, granulation tissue, and fibrosis.  When applied during the first two stages, CPM can ensure the maintenance of normal periarticular soft tissue compliance and prevent the development of stiffness by helping pump blood and edema fluid away from the joint and periarticular tissues.  In other words, CPM prevents the initial or delayed accumulation of periarticular interstitial fluids. 
The duration of each session and the total period of CPM application remain controversial. A Cochrane review reports that short-term use of CPM offers greater short-term ROM benefits, but long-term improvements are yet to be demonstrated to justify its routine use.  This is also supported by the latest systematic review by Yang et al.  which suggests that evidence favouring the routine use of CPM machines is still lacking. However, in order to be able to take full advantage of the clinical application of CPM and truly assess its benefits, one must take account of factors such as the preoperative ROM of the patient, postoperative day of CPM initiation, daily ROM increment, and total application days, all of which are significant independent predictors of CPM efficacy. 
[edit | edit source]
Continuous Passive Motion (CPM) therapy uses machines to move a joint passively and repetitively to a set of number of degrees and movement speed. CPM machines are most commonly applied to the knee, but there are versions for other joints.CPM is most commonly used after joint surgery to prevent joint stiffness complications and for prophylaxis against thrombosis. The time point of CPM initiation, the duration of each session, the total period of CPM application and its effect on long-term outcomes remain controversial.
References[edit | edit source]
- Guidera K.J., Hontas R., Ogden J.A. Use of continuous passive motion in pediatric orthopedics. J Pediatr Orthop. 1990 Jan-Feb;10(1):120-3.
- He M.L., Xiao Z.M., Lei M., Li TS.., Wu H., Liao J. Continuous passive motion for preventing venous thromboembolism after total knee arthroplasty. Cochrane Database Syst Rev. 2014 Jul 29;(7):CD008207.
- O'Driscoll SW, Giori NJ. Continuous passive motion (CPM): theory and principles of clinical application. J Rehabil Res Dev. 2000 Mar-Apr;37(2):179-88. Erratum in: J Rehabil Res Dev 2001 Mar-Apr;38(2):291.
- Gil-González S., Barja-Rodríguez R., López-Pujol A., Berjaoui H., Fernández-Bengoa J., Erquicia J., Leal-Blanquet J., Pelfort X. Continuous passive motion not affect the knee motion and the surgical wound aspect after total knee arthroplasty. J Orthop Surg Res. 2022 Jan 15;17(1):25.
- Lenssen T.A., van Steyn M.J., Crijns Y.H., Waltjé E.M., Roox G.M., Geesink R.J., van den Brandt P.A., De Bie R.A. Effectiveness of prolonged use of continuous passive motion (CPM), as an adjunct to physiotherapy, after total knee arthroplasty. BMC Musculoskelet Disord. 2008 Apr 29;9:60.
- Harvey L.A., Brosseau L., Herbert R.D. Continuous passive motion following total knee arthroplasty in people with arthritis. Cochrane Database Syst Rev. 2014 Feb 6;(2):CD004260.
- Yang X., Li G., Wang H., Wang C. Continuous Passive Motion After Total Knee Arthroplasty: A Systematic Review and Meta-analysis of Associated Effects on Clinical Outcomes. Arch Phys Med Rehabil. 2019 Sep;100(9):1763-1778.
- Liao C., Tsauo J., Huang S., Chen H., Chiu Y., Liou T. Preoperative range of motion and applications of continuous passive motion predict outcomes after knee arthroplasty in patients with arthritis. Knee Surg Sports Traumatol Arthrosc. 2019 Apr;27(4):1259-1269.