Thereis an ( ?over)abundance of literature available on CPM use for the knee. I was mainly interested in it's use following TKR. A couple of studies looked at accelerated implementation of CPM ( ie started in theatre at 70 - 100 degrees) vs control (no cpm) or compared to progressively increasing cpm ( sorry - have lost references!) and found no real benefit. Most of the articles I came across were fairly contadictory in the efficacy or otherwise of cpm vs physio or physio + cpm, but they were pretty old papers (>5 years)If you go to the PubMED website ( just type in pubmed in a search), you will be able to search multiple databases including medline, cinahl etc, and most of the articles have abstracts available online. Pedro has more physio related info, specifically on randomised clinical trials, but not all of it has abstracts available to view online.
I'd recommend looking at the last couple of years to start with, as I'm sure you'll get a heap of results in your search. Good Luck!