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Purpose
Effectiveness
What to Expect
A continuous passive motion machine (also known as a CPM machine) is a motorized device used inphysical therapythat gently bends a joint back and forth to aid with recovery following a joint injury or surgery. It is typically designed for the knee, but there are also CPM machines for joints like the hip or shoulder.
The therapy is called passive because you let the machine do the work. The purpose of CPM is to restore therange of motionof a joint to its pre-treatment level and prevent scarring that can result in a loss of joint mobility.
This article will explain what CPM is and what to expect before and after therapy. It will also describe some of the risks of CPM therapy and whether they actually help.
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What Does a CPM Machine Do?
A CPM machine is used during the first phase of rehabilitation following joint injury or surgery. The motorized device continually moves a joint through a controlled range of motion. The levels can be increased over time as recovery progresses.
The purpose of CPM therapy is to control post-operative pain, reduceinflammation, improve the range of motion, and ensure that the joint heals properly without scarring or adhesions (the sticking together of tissues).
There are different CPM machines used for people who have undergone or experienced:
CPM may also reduce the risk of a potentially dangerous condition calleddeep venous thrombosis (DVT)following knee surgery.
Do Continuous Passive Motion Machines Help?
CPM therapy appears to be beneficial with certain conditions, although it remains unclear if it is necessarily the “best” option overall. This is because some conditions benefit from a more active approach to rehabilitation, particularly if the individual is in good health.
A 2019 review of 77 studies found that intensive CPM therapy was associated with better short-term and long-term outcomes for people withknee arthritiswho underwent knee arthroplasty.
Even so, some people may have less benefit than others. A 2017 study found that CPM was far less effective in people withobesityfollowing total knee replacement compared to those without.
Some experts question whetheractive mobilization(involving exercises that actively bend and straighten joints) may be better for total knee arthroscopy and ACL tear than CPM. Certain CPM therapies, like those used for elbow injuries, have demonstrated little to no benefit.
The American Physical Therapy Association currently advises against CPM therapy after uncomplicated total knee arthroplasty unless a person is unable to participate in active physical therapy.
What Is the Normal Range of Motion of a Joint?
Using a CPM Machine
Before surgery, talk with your surgical team about what your rehabilitation and recovery plan will involve. This includes whether passive or active mobilization will be used and why.
Before Therapy
Your surgical team will prepare you in advance if CPM therapy has been prescribed.
CPM therapy may start immediately in the recovery room after surgery or the day after your surgery. The machine may be used continuously while you are in the hospital, except for when you are having other physical therapy or using the restroom.
After you return home, you may be prescribed a home CPM unit to use most of the day or just a few hours a day. At-home therapy may continue for several weeks.
During Therapy
There are different CPM machines for different joints, but they work under the same principles. The units generally conform to the joint that is being treated. Prior to being strapped in, the healthcare provider or physical therapist will set the machine to a designated speed and range of motion.
Once you are strapped in, the machine is turned on and will move the joint repetitively so that it bends and straightens along a controlled plane of movement.
CPM machines for the knee or hip are mobile devices that are placed on a bed and move the joint while you are lying down. If you have a CPM machine for your shoulder or elbow, you’ll sit in a specially outfitted chair.
During the procedure, you may feel slight discomfort but should not feel outright pain. If you do, let the provider know so that the speed, range of motion, or position of the unit can be adjusted.
After Therapy
You may feel pain after the procedure and may be given pain medication likeTylenol (acetaminophen)or Advil (ibuprofen) if needed.
If at-home CPM is needed, you will be given instructions on how to use the machine. This includes how many hours to use it per day and whether the settings need to be increased every few days or so. If you are unsure or experience pain, let your healthcare provider know.
CPM is often used with other physical therapies. Your physical therapist will monitor your progress and determine which exercises or treatments are best suited based on your progress.
This may include a self-assessment survey like the Knee Outcome Survey Activities of Daily Living Scale (KOS-ADLS). The survey includes six questions about symptoms during daily activities and eight questions about limitations experienced as the result of knee replacement.
If you are not improving as you should, you may be referred back to your surgeon for imaging studies to check if the repair failed or healed abnormally.
Summary
Your healthcare provider may recommend continuous passive motion (CPM) therapy to help you recover from a joint injury or surgery. The treatment involves a motorized device that moves a joint repetitively at a set speed and range of motion. CPM therapy may start in the hospital and continue at home with a home unit.
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8 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.U.S. Centers for Medicare and Medicaid Services.Continuous passive motion devices.Viveen J, Doornberg JN, Kodde IF, et al.Continuous passive motion and physical therapy (CPM) versus physical therapy (PT) versus delayed physical therapy (DPT) after surgical release for elbow contractures; a study protocol for a prospective randomized controlled trial.BMC Musculoskelet Disord.2017; 8:484. doi:10.1186/s12891-017-1854-0American Academy of Orthopaedic Surgeons.Deep vein thrombosis.Liao CD, Tsauo JY, Huang SW, Chen HC, Chiu YS, Liou TH.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;27(4):1259-1269. doi:10.1007/s00167-018-5257-zLiao CD, Huang YC, Chiu YS, Liou TH.Effect of body mass index on knee function outcomes following continuous passive motion in patients with osteoarthritis after total knee replacement: a retrospective study.Physiotherapy. 2017;103(3):266-275. doi:10.1016/j.physio.2016.04.003Wolf JM.Does CPM improve outcomes after elbow contracture release?J Bone Joint Surg Am.2022 Mar 2;104(5):e19. doi:10.2106/JBJS.21.01410Chaudhry H, Bhandari M.Cochrane in CORR: continuous passive motion following total knee arthroplasty in people with arthritis (review).Clin Orthop Related Res. 2015;473(11):3348-54. doi:10.1007/s11999-015-4528-ySt. Jude Children’s Research Hospital.Continuous passive motion after surgery.
8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.U.S. Centers for Medicare and Medicaid Services.Continuous passive motion devices.Viveen J, Doornberg JN, Kodde IF, et al.Continuous passive motion and physical therapy (CPM) versus physical therapy (PT) versus delayed physical therapy (DPT) after surgical release for elbow contractures; a study protocol for a prospective randomized controlled trial.BMC Musculoskelet Disord.2017; 8:484. doi:10.1186/s12891-017-1854-0American Academy of Orthopaedic Surgeons.Deep vein thrombosis.Liao CD, Tsauo JY, Huang SW, Chen HC, Chiu YS, Liou TH.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;27(4):1259-1269. doi:10.1007/s00167-018-5257-zLiao CD, Huang YC, Chiu YS, Liou TH.Effect of body mass index on knee function outcomes following continuous passive motion in patients with osteoarthritis after total knee replacement: a retrospective study.Physiotherapy. 2017;103(3):266-275. doi:10.1016/j.physio.2016.04.003Wolf JM.Does CPM improve outcomes after elbow contracture release?J Bone Joint Surg Am.2022 Mar 2;104(5):e19. doi:10.2106/JBJS.21.01410Chaudhry H, Bhandari M.Cochrane in CORR: continuous passive motion following total knee arthroplasty in people with arthritis (review).Clin Orthop Related Res. 2015;473(11):3348-54. doi:10.1007/s11999-015-4528-ySt. Jude Children’s Research Hospital.Continuous passive motion after surgery.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
U.S. Centers for Medicare and Medicaid Services.Continuous passive motion devices.Viveen J, Doornberg JN, Kodde IF, et al.Continuous passive motion and physical therapy (CPM) versus physical therapy (PT) versus delayed physical therapy (DPT) after surgical release for elbow contractures; a study protocol for a prospective randomized controlled trial.BMC Musculoskelet Disord.2017; 8:484. doi:10.1186/s12891-017-1854-0American Academy of Orthopaedic Surgeons.Deep vein thrombosis.Liao CD, Tsauo JY, Huang SW, Chen HC, Chiu YS, Liou TH.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;27(4):1259-1269. doi:10.1007/s00167-018-5257-zLiao CD, Huang YC, Chiu YS, Liou TH.Effect of body mass index on knee function outcomes following continuous passive motion in patients with osteoarthritis after total knee replacement: a retrospective study.Physiotherapy. 2017;103(3):266-275. doi:10.1016/j.physio.2016.04.003Wolf JM.Does CPM improve outcomes after elbow contracture release?J Bone Joint Surg Am.2022 Mar 2;104(5):e19. doi:10.2106/JBJS.21.01410Chaudhry H, Bhandari M.Cochrane in CORR: continuous passive motion following total knee arthroplasty in people with arthritis (review).Clin Orthop Related Res. 2015;473(11):3348-54. doi:10.1007/s11999-015-4528-ySt. Jude Children’s Research Hospital.Continuous passive motion after surgery.
U.S. Centers for Medicare and Medicaid Services.Continuous passive motion devices.
Viveen J, Doornberg JN, Kodde IF, et al.Continuous passive motion and physical therapy (CPM) versus physical therapy (PT) versus delayed physical therapy (DPT) after surgical release for elbow contractures; a study protocol for a prospective randomized controlled trial.BMC Musculoskelet Disord.2017; 8:484. doi:10.1186/s12891-017-1854-0
American Academy of Orthopaedic Surgeons.Deep vein thrombosis.
Liao CD, Tsauo JY, Huang SW, Chen HC, Chiu YS, Liou TH.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;27(4):1259-1269. doi:10.1007/s00167-018-5257-z
Liao CD, Huang YC, Chiu YS, Liou TH.Effect of body mass index on knee function outcomes following continuous passive motion in patients with osteoarthritis after total knee replacement: a retrospective study.Physiotherapy. 2017;103(3):266-275. doi:10.1016/j.physio.2016.04.003
Wolf JM.Does CPM improve outcomes after elbow contracture release?J Bone Joint Surg Am.2022 Mar 2;104(5):e19. doi:10.2106/JBJS.21.01410
Chaudhry H, Bhandari M.Cochrane in CORR: continuous passive motion following total knee arthroplasty in people with arthritis (review).Clin Orthop Related Res. 2015;473(11):3348-54. doi:10.1007/s11999-015-4528-y
St. Jude Children’s Research Hospital.Continuous passive motion after surgery.
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