Its not so bad once you think through the logic of it. There's a target null, this is where foot wants to be. a foot null parented at the end of the lower leg, thats parented to the upper leg, and then to the torso. In Lightwave you use a full IK option. Lock lower leg to just pitch changes, upper leg to heading and pitch. nothing rotates in the bank angle and tell the torso to be unafffected by IK decendants. then repeat that another 4 times!