The pistol squat is a great exercise to improve hip and spinal alignment and I mean this in the sense of driving force through stable form.
The only issue is that it is very hard. So I have a cue to help you
Pistol squat with a wall behind you and bit by bit try to touch further down on the wall. Keep the knee in line with the outside of the foot and your sternum (chest bone) above your belly button
Let me know how you get on! Your knees, hips and spine will thank you but be warned, this is only for those who can lunge and squat well