Ankles (the foot itself, actually) is closest to the uro-genital system in the cramped quarters of our brain. What I mean is the nerves representing the foot and the sex organs are close to each other in our brain. This may be why a lot of impulse-control poses or meditative poses are used to control our emotions -- which may explain why people find the lotus difficult in certain times of their life. Hey, I don't mean u are over-sexed... Maybe just over-emotional or reactive. If you can't control that, then maybe u used control your ankles and settle into that padamasana..