Leg Breaking Pose

How the name suits this asana.  I have just started exploring this pose in the Advanced classes.  It looks like the movement happens in the knee but I feel the stretch in the hip and hip flexor.

If I understand the pose correctly, eventually my foot should be tucked up underneath my rib cage.

Here is what Leg Breaking may look like one day, in the future.  I don't know the Sanskrit name for this pose, if anyone knows it and would like to share...
Update September 11: the Sanskrit name is Eka-pada Gokilasana.  Thanks Dancing J!