I'm going to the surgeon to schedule my right knee next Monday. Hopefully get it done early October. Did my left 2 years ago. Only problem I had was my knee swelled up with fluid, twice it's normal size. Couldn't bend it past 90*. The PT had her shoulder on my shin and feet against the wall and couldn't bend it. The boss PT said not to worry, when the swelling went down, the knee would bend. My surgeon had a fit. She said if you wait for the swelling to go down, scar tissue would build up and I would never bend it. Surgeon was pretty much right. At 6 months the PT said there hadn't been any improvement and the insurance was cutting off PT. I was at 26* extension and 80* flexion and they said after 6 months I wouldn't see any improvement. I started going to the health club, and the owner, a friend, said I was using all the wrong muscles. He had major knee surgery after an accident. He put me on a new routine and in six weeks had me at 0* extension, straight as a poker, and 100* flexion. I made more progress after 6 months than I did with the first PT. Now I know to be a better advocate for myself. If the right knee starts to swell I'll get the diuretics sooner and make the PT bend the knee.
For my patients, 120° of bend is the pass mark. More than that is nice but not always possible. In any case, you had a dud PT. Waiting for the swelling to go down is a recipe for failure.
Rehab after replacement is simple (but yes, painful). There are only two exercises that you need to do post knee replacement. One is called 'bending' and the other is called 'straightening'. 10-12 reps of each every couple of hours and you need to push it hard enough to hurt. If it doesn't hurt, you're not stretching it. Ice it several times per day for 20+ mins to minimise the swelling. Avoid walking excessively or doing strengthening exercises in the early stages. Why? Because the knee will have a very limited exercise tolerance after the surgery and if you burn through it doing stuff that is not a priority then it will swell more and not respond as well to the stretching that is the key thing in the first few months. As long as you have enough strength to walk steadily, you don't need to work on leg strength. The thing is that regaining strength is not time-sensitive but regaining range of movement is. I normally suggest that people walk as they need to but not to go for a walk for the sake of it. Again, feel free to PM me.
Don't bother with the diuretics. Dehydrating yourself won't influence the swelling within a joint, whoever told you that it would doesn't know how these things work.