defensive stance
 

If the offensive player sets himself at low post, back to the basket and the defensive player stands behind him and sticks his entire leg between the offensive players legs, is this a legal defensive position?

Nothing you stated has anything to do with legality. If there is no contact then you an stand anyway you want. If there is contact then is the defender or offensive player displacing their opponent. If the defender (or offensive player) has to stick their knee in the back of their opponent then the answer is no. Legality with positioning is about contact ultimately and when the contact takes place.

Peace

So in this case, there is no problem with the position until contact is made
http://i376.photobucket.com/albums/o...ond35/BODY.gif
So if the offensive player trips over the defensive players foot, the offensive player initiated the contact so foul is on him. On the other hand, if the defensive player makes contact with the body of offensive player to upset his balance or displace him, then it's a foul on defense.
Have I got this right?

As I said, if there is no displacement and there is no contact where players put their feet is irrelevant. It is only an issue when the contact takes place that displaces or prevents the movement of their opponent. And in your description I would be more concerned with where the knee is to maintain that position as opposed to just where the feet are located.

Peace

If a defensive player simply has their leg between the offensive player's legs like you described, then it's nothing. What usually gets a defender in trouble is when they lift the leg. If it dislodges the post player, you're going to have a foul on the defender.

If the defender trips the offensive player with his leg sticking out like this, I've got a foul on the defender. He's entitled to his normal space; sticking the leg out doesn't qualify.

Agree.

Who initiates the contact is a concept that is sometimes but not always accurate. It can help with the thought process in some cases but you will come to the wrong answer if you make many decisions based only on it.

Instead, it is about who is not in a legal position when contact occurs. A defender's legs or arms are not in a legal position if they are extended outside of their frame. If contact sufficient for a foul occurs with such an extended limb, the defender has committed the foul...even if the offensive player initiates the contact. The defender only gets to restrict the offensive players movements if they are doing so legally.

I think I understand now. No contact, no foul. If offensive player trips over the leg, tripping is called on defense. If the offensive player attempts to move left or right to catch a pass but can't because he runs into that leg, that's impedeing his movement. If the defensive player uses the leg as a means of moving the other player off his spot, that's displacement. Who knew there was so much to watch for in a couple of basically stationary players.

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