If you have the reference picture you're using for the pose, and can post that, it would help... I'll try a crack at it... but one thing to keep in mind... a normal human shin does not go side to side.... go on try it. ;) It'll move a little bit under pressure, but your shin is only meant to bend back. To get the foot on the other knee like that you'll have to focus on twisting the thigh and fiddling with the buttocks.