1. Background

• also referred to as Flexible Flatfeet, Hypermobile Feet, Pronated Feet, Pes Panus, Hypermobile Pes Planus, Pes Planovalgus, and Physiologic Flat Feet
• many infants have fat deposition along the medial aspect of the longitudinal arch of the foot; this fat usually disappears when the infant begins to bear weight on the feet
• flexible flat feet may also be associated with ligamentous laxity within the foot which usually corrects by 6 years of age; therefore the diagnosis of flexible flat feet is usually not made until after 6 years of age
• this condition is to be differentiated from rigid flat feet which is seen in conditions such as Archilles tendon contracture, tarsal coalitions, and cerebral palsy

1. Flexible Flat Feet

• most children are asymptomatic with no functional limitations
• some may present with pain along the longitudinal arch after prolonged activity or with sports
• in the non-weightbearing position:
  • the normal contours of the foot and longitudinal arch are present (i.e., when sitting or in the supine position)
  • the ankles are flexible with a full range of motion
• in the weightbearing (standing) position:
  • the longitudinal arch of the foot falls
  • weightbearing is shifted from the lateral aspect of the foot to the medial aspect producing pronation or eversion of the foot
  • the heel may assume a valgus position creating a planovalgus posture
  • normal or slightly increased subtalar motion
• there may be a secondary tightness of the Achilles tendon
• there may also be ligamentous laxity involving other joints such as the thumb, elbow, and knee

1. Weightbearing X-Rays of the Foot

• loss of the medial longitudinal arch on lateral views
• heel valgus on AP views
• no bony anomalies

1. Supportive

• usually see a significant improvement in the arch as fat is lost from the longitudinal arch
• most show a significant improvement in the arch by 6 years of age due to the progressive correction of the ligamentous laxity within the foot
• do not treat asymptomatic feet with modified shoes or arthoses
• persistent painful flexible flat feet in children and adolescence can be treated with medial longitudinal arch supports

1. Rudolph, A.M., Rudolph's Pediatrics. 19th Edition. p. 1938 (1991).

2. Zitelli, B.J. and H.W. Davis., Atlas of Pediatric Physical Diagnosis. 3rd Edition. p.676 (1997).