@Holly
I am glad your knee feels like it is loosening up. That is, if you mean that in a positive context.
It seems the consensus at bonesmart is mixed on the CPM; some folks love them and some folks don't see the benefit in them. For me personally, it's nice fore a couple of reasons. It really gets a good stretch on my muscles while moving my knee without me having to exert valuable effort at this point. I can set it to a specific ROM setting and know I'm getting a certain amount of bend. I've also found it to provide relaxing comfort at times - I can elevate my leg in the CPM and just turn it off and let it act as a harness for my iced leg.
I had tremendous pain and bruising in my thigh, about six inches north of my knee. I am certain that this was damage done to my quads by the tourniquet they used during surgery. As I used the CPM, I could feel those quad muscles benefitting from it. I could set it on 90 and feel the burn as my quads stretched, but after ten or fifteen minutes, they would loosen up to the point that I could bump up the setting to 95. In my mind, it's been a benefit. You just have to make sure that the company you rent it from sends someone out to train you on how to use it and set it up. As
@skigirl has mentioned, they will slide if you aren't careful and the last thing you want is a CPM machine falling off a bed or a sofa with your leg strapped into it. Also, you don't want to get caught up in the flex setting on the CPM. I was in it earlier today, set to 120. That doesn't mean I'm getting 120 degrees of flexion, though; the real number is probably close to 105-110. But I definitely rely on mine.
There are exercises you can do that are equally as effective as using a CPM. For example, if you have a rocking chair, you can put your left foot on the ground and use it to rock yourself. You will get bend close to 90 degrees doing that, and because it's a rocking chair, you won't have to exert too much energy to do it.
Heel slides is another exercise you can do and I'm sure you're familiar with that one. It takes a little more energy to do those, though.
Bottom line, though, is that ROM just isn't as important as we think it is at this point. I think you had your LTKR a couple of days before mine, and at our stage, our focus should be on reducing swelling as much as possible - RICE (Rest, Ice, Compression, Elevation). That will be the quickest way to achieve greater ROM and extension, but is also the best way to reduce pain and improve recovery time. That just seems to be my experience, though.
I really hope this helped.