I made some comments at recent Boot Camps
on the potentially injurious effects of forefoot varus posting on foot orthotics; we have had a number of threads in the past on forefoot varus
. I have had a couple of emails about what I said, so it’s easier to post a generic reply here:
Forefoot varus is very rare, but when it is present, the rearfoot has to pronate to bring the medial side of the forefoot down to the ground. The traditional approach to dealing with forefoot varus is to use a foot orthotic with a medial forefoot post to bring the ground up to the foot so the rearfoot does not have to pronate.
The point I tried to make was that a forefoot varus post will have two very different effects depending if the foot orthotic was a rigid plastic or a semi-rigid/flexible material:
For the forefoot varus posting to work, it is going to have to dorsiflex the first ray to end range of motion and then supinate the mid-foot joints to end range of motion before it can have any effect on the rearfoot pronation --> potentially injurious due to jamming at end range of motion
The effect of the forefoot varus posts is immediately transferred to the rearfoot to stop it pronating via the rigidity of the plastic --> does not have to move joints to end range of motion to effect rearfoot pronation.
Using a forefoot varus post on anything other than a rigid plastic orthotic to treat forefoot varus induced rearfoot pronation is theoretically and potentially injurious
There are also effects of the medial forefoot posting on the windlass mechanism
There may be other indications for medial forefoot posting when its use is warranted.