Wow, when it happened to me there was no warning at all. It just buckled and thankfully I was near the bed so the fall was broken. I was just waking from a nap on that one. The pain and weakness associated with the other leg happens while I'm awake and actively exercising, so that one doesn't seem to be connected to sleep. I think my GP and one other orthopedic doctor I see are both well versed in this stuff since they both attribute these events to PN. This used to happen to my Dad all the time and it makes me wonder if he had PN and mine is hereditary. This has been an enlightening thread.