That's what I asked a so-called PN expert I saw after I recovered from a broken ankle caused by my left leg giving way. Eight years ago, I was walking to the kitchen after waking up from a nap and out of nowhere my leg folded. I heard a sickening crunch and knew I had a fracture. That break has caused me more grief than PN...the leg/ankle have never been as strong as before. I went from using a cane to using a walker and still do to this day.

The PN expert had no answer whatsoever, couldn't even speculate and offered no causes or theories. Until this thread, I never knew this folding leg/s syndrome affected anyone else w/ PN. It seems to be connected w/ sleep (waking up & going somewhere). Possibly the muscle loses its resilience, strength, etc. during rest. Although my left leg still gives out from time to time, it's not as frequent as it was 9 or 10 years ago. The only way I know to avoid another fall/fracture, is to use the walker or cane even in the house.