I read again ydnar and Si.
It is very true that many muscles are attached to femur some originate in the hip area, some insert into fib/tib. If the femur rotates, some of these muscles are obviously affected, that does not mean that they control the movement.
Here is an analogy: try writing on a blackboard. I hope you use fine muscles located in your hand and forearm to write. Place your hand on your arm and see that you bicep and triceps are slightly contracting from time to time. If you skinny and have developed shoulders place the other hand on different places in shoulder joint and see small movements in rotator cuff, delts, lats, even pecs etc. Still I hope you are not writing with these!
This analogy gives me an idea for an exercise, I will post is separately.
Merry Christmas to everyone.
All tippers and steerers alike I hope all of us have a lot of enjoyment and fun skiing next year.