Overpronation is one of the most overused and misunderstood terms in running and health professional communities, especially when it comes to the use of running shoes. The whole traditional model of the design of different running shoes are based on the concept of the normal or neutral alignment of the foot. Pronation is when the foot rolls inwards at the ankle joint and the arch collapses. Supination is when the foot rolls outwards at the ankle and the arch height increases. These are normal healthy movements that are needed for normal function of the foot. It is how the foot adapts to uneven surfaces and absorbs shock. There is nothing wrong with the motions of pronation or supination.
The term overpronation is used to describe when there is too much pronation. The reason is that this is an issue is that overpronation assumed to be a risk factor for many different running injuries. For this reason, running shoes have design features in them that are supposed to help control this overpronation. These design features include medial heel posts, dual density midsoles and rigid heel counters. These shoes are supposed to be used by those who overpronate. Those who do not overpronate should use cushioned neutral shoes.
The problem with this concept is that the term is overused a lot. There is no consensus as to the cut-off point between normal pronation and overpronation. There is also very little evidence linking overpronation to running injury and if there is any, it is showing that it is only a very small risk factor. Plenty of runners overpronate severely and never have problems. Similarly, there are plenty of runners who do not overpronate that have a lot of problems. Due to this confusion, there has been a recent change in the use of the term and the understanding of overpronation in relationship to running injury and the use of running shoes.