The doctors told me that it could have been as simple as inhaling germs from someone that had a bad cold around me and/or from a minor cut were bacteria entered my bloodstream. Medical procedures (surgeries, ect) can also cause it if germs enter your bloodstream. They also said that it could have taken months after the germ(s/bacteria) attached themselves to the metal parts of the replacement, for it to grow and spread to the tissue (muscle/tendon ect) within the knee, that's when the infection spreads and your body reacts.

I am now very cautious when I do any kind of work, I wear gloves, will definitely clean any kind of cut that I may get to prevent future infections (I was really bad at that), even thou being on antibiotics is suppose to help from now on.