Treating a 15 mm Limb Length Discrepancy with a Full Sole Lift and Orthoses with a Unilateral Heel Lift Here is a patient that was experiencing knee pain from her 15 mm limb length discrepancy, with the left side being longer than the right. I prescribed a 6 mm (1/4") full sole lift to be added into the right shoe sole along with a 6 mm heel lift added to her right custom foot orthosis. Her left custom foot orthosis had no heel lift added to it. You can clearly see the change in gait dynamics fr