ok - let me see if I have this right -
First, you create an IK handle from the left leg hip joint to the ankle joint - make sure it is set to an IKRP solver and that it is also set to 'sticky'. Rename this IK handle 'Left Leg Ik Handle'.
Next create a locator and place it in front of the knee and rename the locator 'Left Knee Locator'.
Select the locator and shift select the IK handle. Go to Constrain>Pole Vector.
Next, create an IK handle from the ankle to the foot and rename it 'Left Toe'.
Select the Left Toe IK and group it to itself. Press insert and hold the V key to snap the pivot to the Foot joint. Press insert again. Rename this group 'Left Toe'.
Select the Left Leg IK and the Left Toe and group together. Press insert again and V snap the pivot to the ankle joint and rename this 'Left Foot'.
Finally, parent the knee locator to the foot group.
You can also go to Display>Component>Selection Handles and select the cross hair in component mode to move the selection handle of 'Left Foot' out of your character so that it is easy to grab and control.
This method was taken from mtmckinley's book. I think that that is right, but I am at work, so can't check.
Hope this helps.