The Continuous Passive Motion (CPM) Machine is absolutely required post surgery for at least two weeks. The recovery protocol states that it is to be used for at least six hours a day. One additional item I learned on my own was to never let it go for too long between sessions. At one point a few days after surgery, I went nine hours between sessions, when I got into the machine after nine hours, I could feel my hip working its way through whatever nasties had settled in during that time period. Things settled out after an hour or so, but I considered that a lesson learned.
Additionally, make sure that the machine is properly fitted in ones sick bed prior to surgery. I worked with the nurse who delivered the machine in an area other than my sick bed, when the time came to use the machine after surgery, I was on a different surface, different clothes and different position. It took several rounds of fiddling with the adjustment controls to get it dialed in properly. This was compounded by the fact that I could hardly move my leg and was I was still somewhat affected by the anesthesia. Additionally, I was still partially numb from the surgery due to nerve bruising, so I was concerned that any damage that did occur, I wouldn’t even notice (right away) (this seems almost comical in hindsight, but at the time, I didn’t find any humor in it at all).