Here is another great exercise that can be done for increasing flexibility in your tkr knee. After reading and hearing about it, I decided to give it a try and it works well for me. It doesn’t require any special equipment.
Sit in a chair with feet firmly planted on ground.
Slide your body forward, keeping feet planted.
Do this until you feel a stretch in your tkr knee.
Hold for as long as you can stand it.
Slide back to starting position.
Hope this works for you as well. Good luck!