I just remembered this. I used to wake up with horrible hip pain every morning, on both sides. After some experimenting I found that if I slept on my side with one leg on top of the other in the exact same position I would have horrible pain. If I don't sleep in that position I don't have it. Occasionally I will wake up at night and notice that my hips are hurting and everytime I am in that position. So I move to a new one and voila no more hip pain. I remember it as being very bad so I am hoping this will help someone.