CPM - Constant Motion Or Constant Pain Machine

One of the larger issues for total knee replacement patients, and physicians, is keeping the patient active and moving so the rehab time is minimized and further health issues not created by the time of immobility. Over the past 2 decades it has become common practice to place the patient's leg into what is called a "constant motion machine" (CPM) and the leg and knee joint are moved immediately following surgery. This is done to:

• minimize atrophy to the surrounding musculature tissue


• increase blood flow into and out of the surrounding tissues


• retard the degree of atrophy one has following immobilization


• maintain the physical actions of the muscles to move fluids away from the injured tissues and prevent edema


• prevent loss of elasticity in the affected tissues

Generally the CPM machine is activated immediately upon the patient being moved to the hospital room following surgery. Over time it has been shown that the recovery time is shortened and pain decreased using one of these CPM machines. The problem is, often due to the pain the operative procedure produces, the CPM machine can be viewed by the patient as a constant pain machine when in fact the overall long term effect is to decrease and prevent pain by getting the patient healed and functional movement restored.

By using interferential therapy at the same time there are even greater advantages for the total knee replacement patient such as:

• interferential treatment minimizes the pain using the CPM machine


• electricity has been shown to accelerate tissue repair and healing


• negative charges of electrotherapy actually move fluids away from the joint and tissues minimizing edema


• interferential therapy increases carryover pain relief so the patient is more comfortable for longer time periods


• interferential therapy aids the muscles to relax and minimizes muscle spasticity which also minimizes pain

When interferential therapy is incorporated, along with a constant passive motion machine, patient outcomes are improved, rehab. time is diminished, and pain is minimal. The patient regains the ability to walk without pain and in a shorter, more pleasant time frame.