Using the CPM

For some time now I have been wanting to make a post about proper positioning in the Continuous Passive Motion (CPM) machine. Well, I am finally getting around to it now that I am actually done using the machine!

The reason I wanted to make this post is that for the first 40 hours of CPM use in the hospital, my positioning was incorrect. This caused unneeded pain and also hampered my progress. Using the CPM is really very simple. However, they started me on it only 6 hours after surgery though, so I was obviously hurting, confused, and exhausted at the time. I think it would have helped if I had known, or if my husband had known, what good positioning should look like. So I have taken pictures.

There are a lot of different CPM machines on the market. I think this guidance will generally be sound advice, but it is only based on my own experience and I am certainly no medical professional.

This picture (GR 2 for visible scar) shows the knee properly positioned. Notice how the high point of the knee is directly above the joint in the CPM.

In order to get into this position, you often have to pull the machine towards you. Before you do that though, pay attention to the positioning of the foot support (GR 1). Notice that it is adjustable based on the length of your lower leg. Make sure it is out far enough that when you pull the machine towards you, it does not jam your foot. At one point in the hospital, this was accidentally adjusted to be too short. When the technician tried to get me back into it, she kept pushing the machine towards me, thinking it was caught on something. It was caught on me! Ouch!

This picture (GR 2 for visible scar) shows bad positioning. Notice how my knee is not directly over the joint. Also,you may be able to see that the angle of my leg is less than in the first photo, even though the machine is set to the same angle. This is how I screwed up in the hospital. If you push it away from you, then you are not achieving as much of a knee bend as the machine indicates. I thought I was up to 35 degrees, but really only had reached about 20.

If not reaching the flex goal isn't enough motivation, it turns out that the CPM will really really hurt if you are in a bad position. It feels much better when flexed (because it isn't going far enough), but when it straightens the leg, it feels like it is hyper-extending it beyond straight. I think this was partially responsible for my worst pain spike episode.

Here (GR 1) is one more photo of bad positioning, but you probably won't notice. Recovery dog is stealing the spotlight in the picture.