Do I Need a CPM Following Knee Surgery?

The argument for a CPM is that patients do have an initial increase in motion following surgery that is more rapid than patients who do not use a CPM. Furthermore, patients who use a CPM following knee replacement surgery are less likely to require knee manipulation (where the patient is given general anesthesia, and the knee is forced into flexion) than patients who do not use a CPM. Also, patients often feel a strong desire to be "doing something" to help their recovery. While CPM may not actually alter the result of the surgery, it can give patients a sense that they are helping their recovery.

No one has shown that a CPM makes any difference in the long run. Time and time again, studies show that within six weeks of knee replacement surgery, patients who use CPM and those that don't have the same range of knee motion. While there may be the psychological effect stated above, there has been no evidence to show that the use of CPM will ultimately improve the outcome of a knee replacement or anterior cruciate ligament reconstruction surgery. That said, there are some specific procedures, such as a release of contracture or adhesions, where a CPM can be an important part of the recovery from knee surgery.

As stated previously, no one has been able to clearly demonstrate any long-term benefit to the routine use of CPM following a knee replacement or ACL reconstruction surgery. Many patients still use a CPM, but those that do not are at no disadvantage. As the studies clearly show, patients are likely to be at the same point within six weeks of surgery regardless of the use of a CPM.

References:

• Pope RO, et al. "Continuous passive motion after primary total knee arthroplasty: Does it offer any benefits?" J Bone Joint Surg Br 1997;79:914–917.
• Lau SK, Chiu KY "Use of continuous passive motion after total knee arthroplasty" J Arthroplasty 2001;16:336–339.