If I am reading what you wrote correctly, you are 10 days out of surgery and at 90 degrees. I am going to give you my honest opinion based upon what I have heard from other TKR patients and conservations between my PT and myself. I believe that I was still using a walker 10 days out and then switched to a cane. My knee was not at 90 degrees that soon, Everyone heals differently and has a different tolerance for pain. But I had a discussion with my PT about a friend who was also recovering from a TKR and going to a different PT. My friend was having trouble with bending, was in a great deal of pain during PT and after PT. This friend also felt like they were being pushed too hard too soon. My PT told me that there are many different ways of working the knee to get range of motion as well as flex back and that it did not have to hurt that bad. Long story short, my friend decided to come to my PT and found that there was a better communication with my PT and that they were no longer pushed to the point of pain. PT is not always comfortable, but it should not hurt the way you described it.