I think that saying my PT sessions "feel like a workout" is a good thing overall. Rolling that IT band roller along my ITR did two things - my active flexion was a couple degrees better afterwards, and I was tired because I had to use both my arms to properly roll it with enough pressure. After all the inactivity of the past seven weeks, feeling sweaty and hot was terrific. And getting to do things like that for a whole hour was a privilege. Each exercise was slow and focused on different muscles each time, and I got to use upper body muscles (pushups against a wall to stretch the calves, abdominals doing leg lifts). At no time do they make me do exercises or stretches that hurt my knee (or anything else; it's really no worse than a good yoga or tai chi session); in fact at the end of each group of moves I generally feel like I could do a lot more and they don't let me.
Also, I think there is sometimes some confusion about what aspects of PT should and shouldn't produce pain. I'm not sure I agree that "PT should never cause pain." It depends on what facet of PT you're talking about.
When I (me, Analysta) talk about painful aspects of my PT, I am ONLY talking about the massage and manipulations (like what WantToBeBiking described). They hurt because the PT is using pressure point manipulation to make muscle knots go away, or manipulating the patella in order to make the ligaments looser, or massaging the scar to break up little adhesions in the incision. Actually, only the pressure point stuff hurts seriously; the others are a good kind of hurt.
That's about half of my usual hour, or a third of it when I luck out and get 90 minutes of PT. The rest of the session is two things: exercises and stretches. These shouldn't hurt much (i.e. there's discomfort and there's hurt). Stretching too far can tear ligaments and tendons and even muscles. Over-exertion of individual muscles can do the same, and can cause swelling. I don't need MORE swelling, I take it easy.
@bdink21, don't let my stuff scare you about starting PT! As far as I can tell, most people's TKR PT is just the exercises and the stretches, and not the manipulations. For exercises and stretches you have the right to stay in the comfortable zone.
@Wanttobebiking, I think it's really useful to know how far you can flex your leg actively, and how far it can be flexed passively (not to the point of pain!). Do you think you can get your PT to measure both? You can have a disappointing active flexion number but if you find out that your passive flexion range is actually 120 degrees, you can feel a lot better about your future!
@gaelan01 --- yeah! talk to you on the 14th or 15th!