Pronation is a normal foot motion. This word refers to the action of the foot as you apply weight through the gait cycle. As the foot strikes the ground, starting from the heel and rolling forward through the arch and onto the toes, a specific series of movements takes place called pronation
. Essentially, the heel and ankle roll inwards after the heel strikes the ground, and as weight is transferred to the midfoot, the arch flattens out.
Pronation is normal; a problem arises where there is overpronation. When a person overpronates, the arch remains flat, and the ankle rolls too far inward as the toes begin to push off. This places increased stress on the muscles and ligaments of the foot.
For more information: Overpronation