Re. Sciatica flare up: I had the same thing - exercises good for the knee were bad for the back. I finally put my hands palm down flat between my lower back and the floor whenever I did exercises in the laying down position. This changed the pressure/stress point for the back and helped a lot. Further down the line, when they ask you to do bridges, ask for an exercise band around the knees. Again, this changes the way your back uses the muscles, and helps. And: if you’re happy with your PT people, ask them for Sciatica-specific exercises when you have a chance. I have been doing a 5 minute set of them daily for 5+years, have not needed a shot in 3 1/2 years.