Three years ago I had knee replacement surgery (the knee cap was not replaced ) I still have a great deal of pain and discomfort especially in the front of my knee. After being on my feet for more than half an hour and have pain that causes me to limp and I have to rest it. Ex-rays show the replaced joint is secure and working as it should be. I have been told that further surgery to replace the knee cap and the cartilage behind it(which seems to have thinned) might be a solution. I realize there are no guaranties it will help and that it is once again major surgery. I am looking for info on this type of surgery and it's effectiveness.