I think the "rods" he's talking about might be doing a revision of your TKR and putting in components with "stems". My tibial component had a "stem" in it...it was about 7" long and went into the bone canal. He decided to use that type of component for stability. However, it sounds like you have a lot more going on than I did/do with the disease you have.
I was right where you are now, Natalie. Couldn't bend, couldn't straighten and was in constant fear of the pain I would get when I would bend it. I also had a full-length brace that had locks on the side that I could set to certain degrees. The only time I changed the settings was when I was sitting down. Other than that, it was locked straight all the time.
After wearing the brace for months and HATING it, my Dr. put me in the removeable cast. (I'll post a pic of it for you) Like I've said before...it was a MIRACLE! Much less pain, and my anxiety level pretty much went away because I wasn't afraid of pain (because there wasn't much) and wasn't afraid that it was going to bend to far.
After months of being in the cast, I decided that life with a straight leg and almost no pain was worth having the fusion surgery. I have no regrets. NONE! Living in the pain that you are in now....I've been there and my heart goes out to you.
I have "degenerative joint disease". Luckily, it has only affected my left jaw, my left knee joint, and my right shoulder. I have TMJ, but it doesn't bother me too much. I've had (2) shoulder surgeries back in the 1990's for dislocation and rotator cuff displacement. My shoulder is fine now..just a small amount of ROM missing. The knee took the brunt of it all.
I think Jo can post a pic of an xray with "stem" in them. I don't know if this is what your Dr. is thinking of, but I can't think of anything else. Maybe Jo can?
If you do not bend your knee at all, does the pain go away? Are you able to walk with the brace locked straight and have less pain? These are key questions you want to explore that might point you in the direction of a fusion. Might. I'll post a pic of my cast, "Peg" below. The cast was set at 10 degree bend.