Hello I am 69 and had tkr 7 weeks ago Tuesday will be 8 weeks. To get your extension at 0, every hour sit on a chair where you can prop your foot up on a coffee table. Keep your leg straight You can put a pillow under your ankle. Do not put anything under your knee. You can put an ice pack on your knee . Keep your leg straight, toes pointed to the ceiling. Watch something on tv that you enjoy. Try to keep it in this position for 10 minutes and add to your time as you can tolerate it. I couldn’t do it very long the first week, but it helped tremendously. Another exercise that helps you can lay in bed. Straighten your leg. Point your toes to the ceiling. Dig your heal into the bed, pushing your knee down with your muscles, and hold for a count of 5. Try to do a set of 10. If you can do them again in an hour do them. My knee felt tight and I was afraid to hurt it a first. You won’t hurt it. I also found that if I iced my knee prior to exercising, I did much better. Keep these exercises up and you will have extension at 0. I achieved it during my first week and continue to have it . I only do these exercises once a day now. The heel digs I do now are 2 sets of 10 once a day! Of course I am doing more exercises now for my ex, which is at 128 now. My other leg has an extension of 140 and it needs a knee replacement. I am working the the knee to achieve 140 extension on it .
The recovery is long for this surgery, but if you stick with your exercises, you will benefit and move on to to the next challenge. Best wishes!