In reply to aleakyboat:
My mum struggles but is not very fit. She is quite short so on rock staircases I guess the steps are bigger for her. Generally she ends up turning sideways.
My girlfriend finds it hard going on her knees compared to uphill or horizontal walking, so she avoids carrying any weight when hiking (I don't mind, honest). Poles definitely help for this by reducing the load on her legs, and I guess improving control/balance.
Not sure how much that helps you, I guess it suggests that downhill walking issues are fairly common. Good luck!
Post edited at 09:28