JC - "The lead knee moving back toward the ball- is this a outward move toward
the ball to help drop the club inside? In other words, is the knee movement different during the down swing than the back swing?"
If you start with a good set-up and make a good turn ( without swaying or losing the brace of the trail leg ), the lead knee will come back on it's own. To start the downswing the lead knee moves forward so that it eventually ends up over the lead foot.
This ideal first move to start the downswing is an aid to helping the arms "drop the club inside", but it is not a guarantee. You must train for that too! The key is that there must not be an unwinding of the torso / shoulders before the lead knee makes this move. From one of my favs:
Hold a straight edge straight down from his knee cap in the 1st pic, then the second, then the third. You can see that in the 1st and 2nd, his torso and arms haven't moved at all. By the third pic, his arms have begun to drop, and his knee is over his foot. Conventional golfers and those who utilize a "hands high" top of swing position will have to make a drop that causes the club to come "more inside" or on a shallower plane. Trail arm alignment solves this for the most part.
Here is a "pretty good" conventional golfer showing the same movement. More flexible, more athletic, but the key move is the same for two very diferent physiques and swings styles: