Hi there! A few reassurances...
It's likely not going backwards; a normal recovery resembles a weird roller coaster more than a straight line upward. On my first TKA, I went through a period during weeks 8-12 where out of nowhere the knee would be too painful to lift off the bed after four hours. Talking 9/10 pain. I had to use my hands and other foot to raise it and swing it. The first steps were awful. By the time I hobbled to the bathroom it was subsiding to 3/10. It wasn't like that any other times but overnight. I just kept up with my walking and ROM. At 12 weeks it literally disappeared overnight!
Generally we ascribe overall increase in pain and swelling to increased activity - too much, too fast - that is aggravating the new, still traumatized joint.
PT bending the joint to get a better number is doing you a disservice. They are overdoing it just for temporary gain, which vanishes as soon as your knee swells up in response to this "treatment" - I saw this effect repeatedly until I stopped allowing it!
Your current ROM is both functional and appropriate for your weeks out. It's FINE!
Here's a very helpful article on our knees' range of motion.
Something I found especially helpful in it is the degrees of flexion required for the following activities:
- 65° to walk,
- 70° to lift an object from the floor,
- 85° for stair climbing,
- 95° for comfortable sitting and standing
- 105° for tying shoelaces.
Heat doesn't reduce inflammation. Inflammation IS heat. Heat is great for chronic pain or muscle aches, but not for post op or post injury swelling and pain. Ice applied for 45 minutes or more reduces swelling and also helps relieve pain. It's safe as long as there's fabric between you and the cold source.