Overpronation is a badly used term that is frequently thrown about in running communities in regards to runner’s feet and the selling of running shoes. Pronation is a natural normal motion that the foot goes through when walking and running. Pronation is the feet rolling inwards at the ankle joint and the mid-foot of the feet collapsing. The body must do this to help adapt to shock.Overpronation happens when there is allegedly a lot of pronation. There isn't any consensus among the specialists just how much is too much and even if it is indeed a problem or not. There are plenty of runners who overpronate that don't have problems.
There is a widespread thought that overpronation adds to the risk for injuries in runners and the evidence is that it does, however it's only a small risk factor and many other factors go into runners having an injury. Due to this alleged risk for injury running shoes have been usually manufactured for mild, moderate and severe overpronators. The most rigid motion control running shoes are designed for the most severe overpronators. Those that have no or minimal amounts of it are thought to be far better off in neutral or stability rather than motion control shoes. This model for the prescription of running shoes is not supported by the evidence and some evidence disagrees with it.
Overpronation is only regarded as an issue if the loads associated with it are enough to harm the tissues. In these cases foot orthoses are generally suggested for the short to medium term and then based on the cause of the overpronation, gait retraining and muscle rehabilitation is used in the medium to long term. Where problems also arise around the use of the term, addititionally there is the problem that there is not one cause of overpronation. There are lots of causes and no one size fits all. Foot supports will work in some people long term. Muscle rehab and gait retraining can work in the long term in others. That's the reason you should figure out the main cause to start with and direct the intervention at this.