If you wake up from knee surgery and feel your leg bending and straightening on its own, do not be alarmed. Your doctor prescribed, and your insurance approved, a continuous passive motion machine, also called a CPM. Orthopedists developed the continuous passive motion machine for immediate exercise following knee replacement operations and anterior cruciate ligament tear surgery.
History
Dr. Robert Salter, chief of Orthopaedic Surgery at Toronto's Hospital for Sick Children, developed the CPM machine in the 1960s. Salter argued that the knee, like all synovial or freely moving joints, requires movement, and that lack of movement causes joint stiffness and deterioration. He explained how movement stimulates synovial fluid, which lubricates the joints and facilitates mobility. The results of Salter's studies indicate that the CPM machine prevents scar tissue formation and shortens the amount of time a patient must spend in the hospital.
Function
The CPM machine was designed for bed rest. It sits on the bed in a vertical position. Keep your leg straight as you place it on the allotted knee pads. Your therapist will help you align the axis of your knee joint with the axis of the machine, and teach you how to use the hand-held console to adjust the range of motion of the exercise.
Movement
The machine, when used for four hours each day, automatically bends and straightens your leg in a slow, rhythmic manner, providing joint lubrication and gradually increasing your range of motion. Some insurance plans do not cover the CPM machine. Exercises such as the quad set and the heel slide provide similar results. The quad set straightens your leg. Sit upright, with your leg as straight as possible, and try to press the back of your knee into the floor or bed. Hold for 10 seconds. For the heel slide, place a towel around your foot, hold the ends of the towel and slide the heel toward your body. Perform these exercises as many times as possible throughout the day.
Milestones
Once you achieve 90 degrees of knee flexion and total knee extension, you no longer need the CPM machine, advises the book "Total Knee Replacement and Rehabilitation: The Knee Owner's Manual." In fact, weight bearing exercises such as cycling, squats and leg presses speed up full recovery and help you gain the strength and range of motion required for a return to daily function or athletic activity.
References
- ContinuousPassiveMotion.org: Biological Concept of CPM
- Maldonado Medical; "Continuous Passive Motion"; Drs. Shawn O'Driscoll and Nicholas Giori
- OSU Medical: "Continuous Passive Motion (CPM) for the Knee"
- "Total Knee Replacement and Rehabilitation: The Knee Owner's Manual"; Daniel Brugioni and Jeff Falkel; 2004
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