Continuous Passive Motion (CPM) Machines

What is a Continuous Passive Motion (CPM) machine? 

A Continuous Passive Motion (CPM) machine is a motorized device that gently moves your child’s joint after an injury or surgery to a joint or nearby structures. 

Keeping joints moving after surgery helps with healing.  

Range of motion is a measure of how much a joint can move. If your child does not move their joint soon after surgery, their range of motion may be permanently limited. This can happen when scar tissue forms and limits movement, or from swelling and stiffness in the joint while it was healing. 

CPM therapy increases the chance that your child will be able to move their limb fully. The CPM machine does all the work, so your child does not have to move their muscles. It can be used while relaxing, eating, or sleeping. 

A CPM can be used to help move joints in the: 

• Hip 
• Knee  
• Ankle 
• Shoulder 
• Elbow 
• Wrist  

Benefits of a CPM machine 

Your care team may recommend that your child use a CPM after surgery (like joint replacement), injury, or if they have limited movement and stiffness in a joint.  

Using a CPM may help a joint recover more quickly and safely by: 

• Moving fluid away from the joint so it does not build up 
• Reducing swelling and pain around a joint 
• Keeping the joint moving to reduce stiffness 
• Reducing the risk of blood clots 
• Helping the tissues to heal better and more quickly 
• Supporting early movement after surgery or injury 

A CPM can be used either in a health care setting or at home.

How a CPM machine works

Each CPM is made for a specific joint. A CPM machine has: 

• A frame with a cradle to hold the joint 
• A motor that gently moves the joint  
• Settings for time, speed, and range of motion 

The machine does all the work. Your child just needs to relax and let the machine move their joint. Your child does not use their muscles to move the joint. This is known as passive motion. This is a safer way to move the joint in early recovery without hurting the tissue. 

What to expect during use

When your child uses the machine: 

• The therapist will set the machine to the desired settings for time, speed, and range of motion. 
• The therapist will place your child’s joint into the cradle of the machine and fasten the straps. 
• The CPM will gently bend and straighten their joint. 

Using a CPM machine should feel like someone is gently and slowly moving your child’s joint for them. They may feel some mild stretching, pulling, or slight soreness afterward. Your child may feel slight pressure from the straps. They should not feel pain or irritation while using the CPM machine. If your child feels pain or irritation after using the CPM, tell your therapist, so adjustments can be made if needed. 

Your child may also hear a soft humming noise coming from the machine.  This is made by the motor on the machine. 

Usually, the therapist will increase the range of motion setting on the CPM machine a little each day.  

Your care team will make a plan for how your child should use their CPM. Usually, this is about 1–2 hours per session, from 3–4 times each day. Sessions may take place for several weeks.  

If you are asked to use the CPM at home, always follow your care team’s instructions and plan of care.  

During physical therapy, your child may be asked to move their muscles on their own, without help from the CPM.  This is known as active motion. 

Possible risks or side effects 

When using the CPM, your child may have: 

• Discomfort or soreness 
• A feeling like something is pulling around the incision (cut)   
• Mild swelling 

How to use a CPM machine

Always follow your care team’s instructions for using the CRM machine safely. Some tips include: 

• Make sure the machine is sitting on a flat, firm surface. 
• Keep the controller within reach so that you can adjust the settings if instructed. 
• Position your child’s body and place the joint in the machine exactly as instructed.  
• Make sure the straps fit snugly, but not so tightly that they cause pain or irritation.  
• To help protect your child’s skin, place a soft cloth between the skin and the straps if needed.  
• Check the skin for irritation after CPM use. 
• Put the machine at the settings as instructed by your care team.  
• Do not change the settings unless you are told to do so. 

Cleaning and care of your CPM machine 

After each use, clean the CPM straps, padding, plates, and cradle with a soft cloth dampened in soap and water or use a disinfectant wipe.  

Do not get the equipment too wet or get moisture in the motor. 

Inspect the CRM machine regularly for any signs of wear, such as worn straps or padding, cracks, damage to the power cord, or clicking sounds.  

Follow your therapist’s instructions for cleaning and maintenance. 

When to stop using CPM and call your care team

Stop using the CPM and contact your care team right away if your child has: 

• Sharp pain, pain that does not get better over time, or pain that will not go away, even if the range of motion is decreased on the CPM. 
• Increased swelling 
• Numbness or tingling 
• Blisters or sores on their skin 
• Redness, warmth, or fluid coming out of an incision 
• A joint that “locks up” or does not move as usual 

Do not use a CPM machine if: 

• Movement might damage an area that is repaired 
• There is an infection near the surgery site 
• There is severe swelling or pain 
• The area is numb 
• The skin is irritated or damaged, or there is a wound

If your CPM machine isn’t working right, take it off and unplug it. Do not use it again until your therapist checks it. 

Contact your care team with any questions or concerns about using the CPM machine.

Questions to ask your care team 

• Why does my child need to use a CPM machine? 
• How long should my child use the CPM machine? 
• What settings should I use?  
• What symptoms or problems should I watch for and report right away? 
• When should my child stop using the CPM machine? 
• Who should I call if I have problems with the CPM machine? 
• How do I return the CPM machine when it is no longer needed? 

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