What are the most common symptoms of flatfoot?

May not be any... Flat feet do not, in and of themselves, hurt. Sometimes they can affect ankle, knee, and hip alignment. Some people never have any problems with flat feet, while others may be predisposed to developing more stress through other joints ( most commonly, the knees). If you are having pain, get it checked out by a sports medicine physician.
Flat feet. Foot pronation (inside of foot caves inward when standing) foot pain/fatigue easier than other people when walking or running.