About the Lounge Doctor, keeping the legs straight, and PT...
The "legs must be kept straight" thing is an obstacle we all encounter because the wisdom of nurses -- bent legs (like sitting in an airplane) for long periods impedes blood flow and makes them prone to developing blot clots -- is not the same as the wisdom of TKR recovery. TKR knees, through years of arthritis or other issues, have developed shortened tendons. In most cases, those tendons will eventually stretch back to normal after TKR. But until they do that... the darn things hurt! It's painful to lay with our new knees perfectly straight.
It's also not necessary. You don't have to have perfectly straight legs to prevent blot clots. Just not hours of deeply bent legs. A small bend does not impede blood flow and is perfectly safe. But most hospitals have the "legs must be straight" thing as gospel.
That's why my first week, starting in the hospital and then in rehab, were part torture. It wasn't the PT (more on that later) but my battle with staff to elevate (they thought that meant putting thickly rolled towels under my ankles) AND have a little bend... like the one of my Lounge Doctor waiting at home. It was a battle I fought by getting rid of those towel rolls and bending my knees just a little, very little, only to the point of comfort, at every opportunity. Because I was progressing so well, the nurses just let me do what I wanted. I was SO HAPPY to go home at last and use my foam wedge with a bend. It was so comfy, and I could sleep with it, and I elevated all the time (seriously, about 20 hours a day) for the next several weeks. Ice and elevate, that's what I did.
I also did PT. Many people here did none at all, but I did some. My OS wanted it (with restrictions such as no weights, machines, etc.) and I figured as long as it was useful to me, and the therapist didn't force my knee EVER, I would give it a go. The PT at rehab was gentle, focused on function, and consisted of stretches over which I had full control (except for one therapist who was aggressive and who taught me what NOT to allow). At rehab I did lots of walking practice, stairs, and other practical things.
You will definitely leave the hospital knowing how to get in and out of bed, chairs, cars, walk, go up and down stairs using a cane, and bathe yourself. I was two days in the hospital, and they taught me those things before I headed to rehab (where I learned even more tips, such as how to transport things safely in a kitchen).
My outpatient PT (also a concession to my OS, whose work was performing so excellently I gave him the benefit of the doubt) was a constant battle with my therapist, who wanted me to do leg presses so insistently I wondered if he was on commission. But I stuck to my guns, did only the exercises my OS stipulated in his virtual guides (again with a couple exceptions that taught me why those exercises were bad for my new knees) and my progress was BETTER than his other BTKR patients, who were there at the same time I was.
So my advice would be to work with your PT(s) but keep to the wisdom that if what you're doing is causing pain (not just discomfort, even lots of discomfort, but pain), that's your knee telling you to stop doing it. You can always try the exercise again a little later, after a week or two, and then it might be just fine. The PT's job is to advise; yours is to be the decision-maker. It's your knee. You decided whether or not to have the surgery. You decide whether or not to do the exercise.
It need not be adversarial. Your PT just needs to respect your judgement.
How cool about Carlos! I have a Bolivia connection myself. My first husband was from La Paz, and our oldest son's wife is from Sucre. I have lots of family (through these marriages) in Santa Cruz also. Bolivia is a beautiful country with amazing people. I spent a portion of my twenties living in La Paz and Irupana where I was, for a time, the tallest person around and in great demand for playing basketball.