I had a similar problem after my TKR. I had constant pain and swelling, and my knee never felt right. I got tested for metal allergies after everything else was ruled out. The test result came back as "reactive". It wasn't highly reactive, but it was reactive, so since things were not improving, my OS and I decided on a revision with a nickel-free implant in case that was the cause, even though there wasn't an extreme reaction to nickel. I have always had a big problem with nickel earrings, so knew that I do have a nickel allergy or intolerance to some extent. Anyway, much to my doctor's surprise, when he got in there and was about to start chipping out the implant, it fell out on it's own. It wasn't bonded to the cement and was loose. The tests hadn't shown that it was loose, but now we knew the cause of my problems. We'll never know if my nickel reaction was a contributing factor or not, but we do know I wasn't imagining things and I did need the revision.