Excessive Weight Bearing Compromises Foot Structure and Function Across the Lifespan - The Mechanobiology of Obesity and Related Diseases - page 145

Fig. 1 Structural changes to the developing child's foot. a The flat and padded appearance of the
feet of 7-week old infant. b After a year of weight bearing, an indentation is evident on the medial
aspect of a young child's foot. c As a mature gait pattern is established, the longitudinal arch
becomes more evident at around 3-4 years of age. d Development of the foot is complete at
approximately 18 years of age
development is not complete until approximately 18 years [ 6 ]. Furthermore, if
ligamentous laxity within the foot is not resolved, a position of extreme pronation
(also known as a lowered longitudinal arch or flat foot) may develop, leading to
problematic adolescent or adult feet [ 7 - 9 ]. Staheli [ 10 ], however, reported that flat
feet were commonly displayed in both infants and children and could even be seen
normally in adult feet without pathological consequences.
Flat feet, medically termed pes planus, are caused by loss of the medial portion
of the longitudinal plantar plate, which is described below [ 11 ] (see Sect. 3 ). It is
the most common foot deformity in industrialised societies with 60 million
Americans or 25 % of the population of the United States of America reporting to
have the lay-term ''fallen arches'' or flat feet [ 12 ]. This abnormality has the ten-
dency to make the foot supple (or prone to collapse) because the foot lacks the
ability to supinate in order to form a rigid lever during push-off in gait [ 13 ]. There
are many types of flat feet—including relaxed flat foot, congenital flat foot and
rigid flat foot—that are caused by a variety of mechanisms. Relaxed flat foot is