My first response to your post is: I'm wondering if you might have an infection. I'd call your surgeon or whomever is covering for him or her, now.
My second response is that maybe the PT is too intense/damaging to such newly traumatized tissue. In my 1+ year adventure into the world of TKRs I've learned that there are basically 2 approaches to PT. One is "no pain, no gain," the other is much gentler. The high pressure PT "circuit" didn't work well for me and I had so much pain afterwards that I would miss the subsequent session. I found a gentle DPT who has helped immensely.
I hope you'll post again after you speak to a doctor.