I think this ligament is a distal fascicle of the anteroinferior tib-fib ligament and it is orientated parallel and distal to the anterior inferior tib-fib ligament. Co-existent instability in the ankle region can result in the lig causing antero-lateral impingement.

Not sure what movement you are talking about - would guess tib/fib external or internal rotation on a fixed (dorsiflexed) ankle may be problematic?

Try taping (possibly a circumferential 'syndesmosis type' method - difficult to tell withoutout knowing more about the injury), activity modification, possibly later corticosteroid jab and very very very last resort arthroscopic Sx (Oops! Nickhedonia will kill me if I don't mention unilateral spinal mobs)

cheers

physioz