Contoured to restore TNJ & 1st Ray function The Prostep foot orthosis is contoured to improve the ability of the low arch foot to function correctly and eliminate the cause of pain. By physically supporting the ST (sustentaculum tali), reducing 1st Ray pressure and custom posting the heel and forefoot, forces are normalised, function is restored and symptoms resolved. Prostep can be modified using the 0°, 3° or 5° medial or lateral posts.