How Does It Happen

Hospitals have a reputation for being clean and germ free. The operating rooms are supposed to be sterilized clean and safe. I want to know with all the money they charge just for a doctors visit they should be spotless clean. Why is it then that a lot of surgery patients are catching infections before they leave the operating room or in their rooms. Since the surgery is wrapped in bandages how do they get the infection. I had knee surgery 3 months ago and was transfered to a nursing home for rehabilitation. The nurse at the home saw infection in my knee the day I got there. I was transported back to the hospital for a IV antibiotic trearment. Well it's been 3 monts now and my knee still isn't healed enough than I don't need a walker or a cane to even walk.