While the evidence of the efficacy of foot orthotics is really clear on them working, what is not so clear is if they are really needed over the longer term or if they should just be a short term intervention. Like a lot of other clinical decisions, there is no evidence to guide this, just a lot of rhetoric and propaganda, especially from bloggers with no clinical experience! There are plenty of people who have worn orthotics long term and none of them have become infertile, got brain damage, gone bald or got heart disease form wearing them over the long term. There are also plenty of people who seem to only need to wear their foot orthotics in the short term and they are fine and have no more problems.
So, should they be used in the long term or only as a short term measure? Firstly, there is absolutely nothing wrong with the long term use of foot orthotics. There is no evidence of any harm from them. Two studies have shown that they increase muscle strength and one study has shown that they do not weaken muscles, so any one who makes the claims of them weakening muscles are talking through a hole in their head, as the evidence on that is really clear. They certainly can’t point to any evidence to support what they are saying. Surely, if someone is going to make such claims, then the onus is on them to come up with the evidence to back up the claim.
So when should they be considered short term interventions vs a long term intervention? In the context here of overuse injuries¹ being due to cumulative loads in the tissues beyond what the tissue can take, foot orthotics are a good way to reduce that load in the tissues to a level that the tissues can tolerate. What is wrong with that? Problem solved. If someone is happy to keep wearing them knowing it won’t weaken the muscles nor make them infertile, bald or give then heart disease, then what is wrong with that? Keep in mind that in some injuries and in some tissues, foot orthotics can not reduce the load, so should probably not be used in those situations (unless there is another compelling and rational reason to use them).
What if they don’t want to wear them over the medium to longer term? That is fine and there is nothing wrong with that. The only way for this to happen is to increase the ability of the tissues to take the load or find other ways to reduce the load on the tissue that is a problem. Keep in mind that this is not a short term measure and is more of a medium to long term measure. If someone is in pain or having a problem with an injury today, then the short term use of foot orthotics is wise (assuming that they are properly designed to reduce the load in the problematic tissue) and they do not want to wait until the medium term strategies have a chance to work. The ability of the tissues to take load can be enhanced with things like the emerging concepts of mechanobiology (eg eccentric loading exercises). This takes time and effort (as compared to foot orthotics which are easy!). Other interventions can also be used to reduce the load in the tissues that are problematic such as changing the running form and gait retraining, but this is more of a medium to longer term measure.
When might foot orthotics have to be worn in the longer term? They will need to be used if the tissues can not be adapted to the load. This can probably happen in two situations: One, when the loads are just so high that there is no way for the tissues to adapt to those high loads, so a more long term reduction in those loads is needed with foot orthotics (invariably this is due to higher joint moments from variations in joint axes positions; or a problem with high body weight). Two, the runner does not comply or is not willing to carry out the exercises needed to help adapt the tissues. Additionally, some people are just more comfortable wearing them. There are no problems with that.
It all comes down to personal preferences in the context of what evidence there is.
As always, I go where the evidence takes me until convinced otherwise.
¹Obviously we are not talking about the type of foot orthotics used for treatment and prevention of plantar diabetic foot ulcers, painful plantar rheumatoid nodules, etc