Pat, I'm sorry if your medical personnel are using the word "reject" to you with what you're going through. They are testing you for a metal allergy. If you are allergic to the specific metals used in implant material, you will have an allergic reaction. I know it's just semantics, but the word "rejection" really isn't the same as an allergic reaction.
Since you had the allergic reaction to metal used in your previous procedure, it's unfortunate that your current surgeon didn't pick up on that and do some testing on you before you had your TKR. I'm glad you're getting it now, though. There are options for implants once they know which metals you are allergic to. You'll need to keep this fact in mind for any future procedures you might have an always insist on being tested first.