Arch supports or the “arch support” variable in foot orthotics simply support the medial longitudinal arch of the foot. The need for arch supports was based on the traditional model of the arch of the foot being lower and needing to be supported. That is now a bit of an outdated concept. That does not mean that arch supports are not helpful for problems with the feet that are related to a flatter or lower medial longitudinal arch – it just means that a lot more is known about the foot now and its a lot more complex than just supporting the arch.
Technically, an arch support raises the arch of the foot in the sagittal plane. Foot biomechanics is complicated and the foot functions in all three body planes, so more recent concepts of foot orthotics address foot biomechanics in all three body plane, not just the one the involves the arch of the foot collapsing.
The arch of the foot collapsing is more of a symptom than a problem. The flattening of the arch of the foot is better managed if the treatment was directed at the cause of that flattening rather than just treat the symptom with an arch support. This is also based on the assumption that a flatter arch is always a problem, when it certainly isn’t and not all need treating. The cause of the flatter arch may be a muscle strength problem, in which cases things like the short foot exercise may be indicated. The cause may be a forefoot varus which has no other option for its management than foot orthotics. The cause may be tight calf muscles in which case it is best treated with calf muscle stretching. The list of potential causes is quite long and it really is important to determine the cause before deciding on which is the better treatment option so as not to waste time and resources.
There is no simple answer to the question, what do arch supports do? It way more complex than that.
