A Continuous Passive Motion (CPM) machine is a motorized device designed to gently and consistently move a joint through a specified range of motion without any effort from the patient’s muscles. This passive movement is typically prescribed following orthopedic surgery, such as a total knee replacement, to maintain mobility and aid in recovery. The machine helps prevent joint stiffness and the formation of excessive scar tissue, which can limit long-term flexibility. The CPM device also promotes blood flow to the surgical site, supporting the healing process and potentially reducing swelling and pain.
Preparing the Machine and Limb Positioning
The CPM machine must be placed on a firm, flat surface, such as a bed or the floor, before starting any session. Securing the machine base against a stable object, like a headboard, prevents shifting during operation. Proper setup requires adjusting the device’s frame to match the patient’s limb length above and below the joint.
The most precise step involves aligning the body’s joint axis with the machine’s hinge mechanism. For a knee CPM, this means positioning the center of the knee directly in line with the machine’s bend point. Correct alignment ensures the movement is anatomically accurate and avoids undue stress on the healing joint.
Once aligned, the limb is secured onto the machine’s carriage using comfortable, padded straps. Fasten the straps snugly enough to maintain alignment but loosely enough to avoid restricting circulation or causing discomfort. The patient should be lying down or comfortably supported, ideally with the back propped up no more than 30 degrees.
Understanding the Control Panel and Settings
The CPM machine’s function is managed through a handheld control unit, which allows the user to monitor and adjust the movement parameters. The most important setting is the Range of Motion (ROM), which defines the maximum flexion (bend) and extension (straightening) the machine will achieve. These limits are strictly determined by the prescribing physician or surgeon and must not be exceeded.
The control panel displays the current angles and allows for incremental adjustments to the ROM, typically by single degrees. The extension setting is often set to zero degrees (full straightness), while the flexion setting is gradually increased as recovery progresses. Most machines also feature a speed control, which determines how quickly the joint moves through the prescribed cycle. A slow and steady speed is generally recommended, especially when starting use, to ensure comfort and controlled motion.
Many control units include a dedicated patient stop button, often colored red, which immediately halts the machine’s movement. This safety feature allows the patient to stop the session instantly if they experience sharp pain or discomfort. Some devices also permit setting a pause time at the maximum flexion or extension points, which holds the joint in a stretched position before reversing the cycle.
Safety Guidelines and When to Stop Use
The prescribed usage protocol generally involves using the CPM machine for several hours per day, often in sessions lasting up to two hours at a time. This daily duration and frequency are determined by the specific surgical procedure and the individual patient’s rehabilitation plan. Adherence to the doctor’s protocol is necessary for achieving the desired therapeutic effect.
Always check that the power cord is securely plugged in and positioned to avoid tripping hazards or accidental disconnection. Keep loose clothing, hair, and fingers away from the moving parts during use. Never attempt to manually increase the Range of Motion beyond the limits set by the healthcare provider, as this could strain the healing tissues.
Immediate cessation of use and contact with a healthcare professional is required if certain signs appear. Stop the machine and call your doctor if you experience sharp, intense pain that does not resolve upon stopping the device.
Concerning Physical Signs
- The affected limb feeling unusually warm, tender, or increasingly swollen.
- Any new drainage or redness around the incision site.
- Numbness, tingling, or a pale, cool appearance of the limb, which may signal circulation problems.