Now, its pretty easy to set up a basic pole vector controller; just select the controller and then the IK handle. The problem is if you move the leg about you might have to counter-animate. If you want to make sure it follows your foot controller and IK handle this is a handy and quick way to make it happen!
select knee controller then IK handle and constrain>pole vector
put knee controller under a group (cntrl+g)
center pivot on group
Select IK hip joint, foot controller, and lastly the knee group (group above the pole vector control)
the controller popping behind the knee is normal, don't worry about it!
select IK hip joint, shift select knee group (the group above your pole vector controller)
aim vector is Y = 1, up vector y=1 as well (default)
select the curve contoller (not group) for the pole vector knee and move forward
freeze transforms on it
now you can adjust the foot controller and your polevector controller will follow!