Hello, thank you for posting your question on Healthcare Magic!
It sounds like you are very concerned about your fiancee's health. You should know that physician's do not consider a temperature to be a "fever" until it reaches 100.4F or 38C. He should continue the antibiotics.
As far as the redness
along his tibia
, it is difficult to give you a good opinion without seeing it. If this redness is in the region of the incision for the knee surgery
, it is very likely normal at this point. It will take some time for the skin to heal. If it is further down the leg, it could represent another infection of some kind. I would recommend monitoring him closely for TRUE fevers. If he begins to have a fever or the redness on his leg becomes worse, he should be seen by the surgeon who did his knee replacement
Wishing you the best of health,