Hi there .... Yes, about 10 years ago I had 2 meniscus surgeries, then finally a RTKR about 5-6 years ago which continued to give me problems, pain, swelling, etc. So, about 4 years ago I had a revision. Truthfully, it has really worked out very well. When the weather is going to be bad, and the barometer drops, then it hurts, so then I rub it with Arnica cream and wear a support over it. It has done quite well since the surgery, and I did really work it when I went to P.T. One thing you mentioned, and this could be at least part of your difficulty .... you said "fat" .... if you weren't joking, I know that being overweight can really cause the knee to not heal well and also buckle. My sil's mother is short and quite overweight. Her knees pain her so much she can hardly walk. The Orthopedist told her he will not do knee surgery until she loses a substantial amount of weight, which she seems unwilling to do. I really don't want to be insulting, but if you truly are overweight, that could definitely be causing your problem.
Take care ..... abby