For 11 years I have had knee pain and I have had injections every 6 months for that period. They are really hurting and the one doctor said I need to have the left knee done soon but, I have to be mentally ready. I have heard terrible stories and then I don't know which doctor to go to. I'm so worried. Any help? Also, I'm thin and that has been a plus the doctor said. This problem is caused by years and years of high impact aerobics.