Flatfoot in the Adult.

Flatfoot in the adult has long been a poorly understood "wastebasket" diagnosis, often used to unfairly deny asymptomatic individuals equal employment opportunities in our society. Now that flatfoot has been classified into a variety of congenital and acquired conditions, the parameters for assessment have been well defined, and rational treatment protocols have been established. Clearly, if the foot painlessly supinates/inverts to become a rigid lever for push-off and pronates/everts to absorb stress during stance, then it "functions normally" no matter what the height of the arch. However, the biomechanically offset position of pes planus with excessive heel valgus coupled with rigidity or instability can alter the connected interplay of the bones of the foot and weaken the entire kinetic chain of the lower extremity. Careful clinical and radiographic evaluation, coupled with a thorough understanding of the anatomy and biomechanics of the foot, will allow accurate evaluation and appropriate treatment.