The optimal arch height for a patient with functional flat foot may depend on the goals of orthotic management. Studies suggest that arch height directly affects excessive motion, but that controlling dynamic balance may require a more tailored approach.
The interaction between the foot and its environment is critical in all forms of gait. During running, the foot provides a flexible landing structure that is adaptable for placing and accepting weight during initial contact. Then during push off, the foot provides a rigid structure to permit the transmission of forces created by the lower leg muscles to propel the body forward. In walking, the forces are much smaller, but now the foot acts as a neuromechanical conduit that provides both sensory information and the transference of mechanical forces to maintain the body’s stability. All of these functions occur in all forms of gait, but the prominence or importance of each of these roles is determined by the type of gait considered. Due to the importance of this type of interface between the foot and its environment, the application of in-shoe foot orthotics is critical to preserve these functions.
Flatfoot deformity or pes planus is the most common foot pathology in patients of all ages. The deformity may be associated with discomfort and pain, instability, serious foot, ankle, knee, and lower back joint problems, misalignments, and postural strain. However, individuals with this deformity can also be a symptomatic. Within pes planus, the functional (sometimes termed “flexible”) flat foot (FFF) is defined as a hypermobile foot with excessive hindfoot valgus and minimal medial-longitudinal arch height when weight bearing. Most often flat foot deformity is treated with custom orthotics to aid in arch realignment and to provide stability.