My mom is out of surgery. Her knee replacement has been removed and a spacer has been put in for the next two months. The doctor said she has very strong bones and that sometimes with weak bones a bit of bone comes with the implant and they have to do reconstructive surgery. Happily, they did not have to do that.
Her knee was indeed filled with an infection, so it’s very good they caught it when they did. Now we wait 2 months before they can put a new knee in.