Why is My Doctor Prescribing a CPM Machine?

CPM machine

If your doctor has prescribed a CPM machine, then you’ve had a total knee replacement.  CPM stands for continuous passive motion.  It came into use in the late 1970s when a doctor named Robert B. Salter, from Toronto, Canada, discerned that immobilizing the joint following surgery wasn’t the best course of action.

The goal of the CPM machine is keep your knee and its structures moving.  We all know that movement is good for us, but following surgery, therapeutic exercise can be challenging.  While you should still pursue physical therapy to fully regain your mobility, the CPM can help.  You can’t be expected to move your knee for hours at a time and so, the CPM does it for you.

If you’re asking yourself “Why is my doctor prescribing a CPM machine?”, it’s because she knows that joint needs to be kept in motion to have its best chance to heal and get you moving around normally again.


The therapeutic effectiveness of the CPM machine resides primarily in the ability of perpetual motion to regenerate cartilage growth.  This is achieved by maintaining the flow of blood and essential nutrients to the joint.

The CPM also helps you avoid post-surgical problems like stiffness, swelling and soreness.  It reduces the instance of scar tissue forming, which may interfere with healing, and improves mobility and flexibility in the healing process.

What’s the Routine?

Your doctor’s advice will probably have you using your CPM machine 2 or 3 times per day, for an hour or 2 at a time.

You’ll need to use the machine for 2 or 3 weeks after you leave the hospital, but you’ll be started on your new regimen while you’re still there, with the help of a physical therapist.

Are You Covered?

Most insurers and Medicare will cover the machine for total knee replacement and for ACL surgery (anterior cruciate ligament, which is part of the knee).

If the machine is prescribed for other joint surgeries, reimbursement is awarded on a case-by-case basis and this varies significantly from insurer to insurer.  Your doctor will have confirmed that you’re insured for the rental for this device.

Some Guidelines

  • Even if your doctor has prescribed frequency of use, using your CPM machine as often as possible (including when you’re sleeping) is a best practice for total recovery.
  • Be sure your CPM is positioned securely.
  • The machine should be positioned in a clean, dry area.
  • Don’t fiddle with the controls. They’re set by your doctor or therapist.
  • It’s not a toy, so keep the kids away from it.
  • If you encounter any pain while using the CPM, stop treatment immediately and contact your doctor or therapist.

Be sure to follow up with your doctor or therapist regularly to ensure that you’re on track for recovery and to review any questions you may have and remember – follow doctor’s orders!

Obility’s mission to provide all you need to feel better.  Whatever better means for you, it’s our wish that you get there.  Let us join you on the journey.

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