Continuous Passive Motion after Knee Replacement: Does it Help?

You may have heard about the use of continuous passive motion (CPM) after total knee replacement (TKR). It uses a mechanical device that moves the knee through a preset range of motion. The idea is that early and constant motion after surgery will help the joint heal faster.

But does it? Results of many studies don’t agree. Some say that CPM helps speed recovery while others say it doesn’t. In this study three groups of patients were compared. The first group used CPM in the standard way. They started with the knee straight. The CPM was set to bend and straighten the knee. The second group started in flexion and moved into extension. The third (control) group didn’t use CPM at all.

The two CPM groups used it twice a day for three hours over five days. Everyone in all three groups had the same physical therapy program after TKR. Results were measured by range of motion and knee function. Everyone was followed at five days, three months, and one year after the operation.

There were some differences among the groups when measured at day five. The second group that started in flexion had more motion than the other two groups. All other measures were the same for all three groups at three months and again at one year. Patients in all three groups had the same length of hospital stay and number of rehab visits.

The authors say their results agree with some studies and disagree with others. Although one CPM program increased flexion early, the end results were the same for everyone. This study agrees with others that suggest CPM isn’t needed after TKR. An aggressive physical therapy program is all that’s needed.