Hi and welcome!
My mother's PTSD flamed after a surgery. She wasn't dx'ed until then, in fact.
I think there's something proven about the experience in combination with the stress and the anesthesia that can trigger PTSD episodes, and even bring out PTSD that wasn't previsouly known to be such because it brings out so much.
There's several of us here who live with PTSD and will listen whenever you need to talk.
Again, welcome.
KD