Yeah, it can sort of come out of nowhere (my mom had it. I don't seem to but... *knocks wood* they say it can be heredity so I never take not having it for granted).

My first guess before seeing you suspecting RA was "inflammation" but in a long story short sort of way, it's almost the same thing (wherein the immune system simply goes off the wall attacking itself via RA).

My mom took no meds ever for RA (they didn't really have them when she got it; by the time they did she really didn't want them, despite how bad it was; she'd adjusted, I guess) so if it ever gets that far with you (hope not) I have no idea on that.