Flat Feet (Acquired Flexible Flat Feet)

Key Points:


Hypermobile flexible pes planus is usually due to ligamentous laxity.  The medial longitudinal arch collapses, the hindfoot is in valgus, and the forefoot is abducted and supinated relative to the hindfoot.  In 27% of patients with flexible flatfoot, there is an associated heel-cord contracture that is characterized by restricted ankle dorsiflexion (Bouchard, 2014).


The epidemiology of acquired flatfoot is largely unknown because many affected patients are asymptomatic and do not seek medical attention.  The literature suggests that the prevalence is at least 20-23% by adulthood (Harris, 1947).  A study of 835 children in Austria found the overall prevalence to be 44% (Pfeiffer, 2006).  The male to female ratio is 2:1 (Bouchard, 2014).  Obese children are 3 times more likely to develop acquired flexible flatfoot than those with healthy weight (Bouchard, 2014).

Clinical Findings:

Most children are brought to the orthopaedist because parents are concerned that a foot deformity may later cause pain and/or disability as an adult (Bouchard, 2014).  A careful history must be obtained, and the location of the foot pain may help guide management.  Flexible flatfoot and generalized ligamentous laxity can be familial, and a thorough family history is important.  Typically, pain is located under the plantar-medial midfoot and occasionally is in the sinus tarsi, as is more common in patients with an achilles contracture.  Pain is usually related to activity (Bouchard, 2014).
A low or absent arch is observed with hindfoot valgus while weight-bearing.  With single toe heel rise the arch elevates and hindfoot valgus will change to varus (Skaggs, 2006).  The arch may also be observed when the foot is in a non-weight bearing position, such as when the foot dangles off of the exam table.  The Jack’s toe-raising test or dorsiflexion of the great toe can recreate the arch which suggests a naviculo-medial cuneiform sag (Mosca, 2014).  The examiner is able to test for hindfoot mobility by cupping the heel then inverting and everting the hindfoot (Skaggs, 2006).  A Silfverskiold test is performed to evaluate for an equinus contracture (Mosca, 2014). It is important to hold the subtalar joint in a neutral position to assess true motion of the talus in the ankle joint (Bouchard, 2014).  Often patients may have mild abduction of midfoot in the weight-bearing position or the “too many toes” sign.  It is also necessary to assess relative supination of the forefoot with respect to the hindfoot and its rigidity. This is essential for understanding the foot mechanics for both orthotic and surgical management.  Examination of the patients’ shoes and inserts can help as asymmetric medial wear of the sole and heel are common (Bouchard, 2014).  Lastly, overall limb alignment must be assessed as knee and ankle deformities may influence foot position. 

Imaging Studies:

Radiographic evaluation is only indicated when pain exists and includes weight-bearing AP (antero-posterior) and lateral views of the foot.  A non-weight bearing oblique of the foot can assess for a calcaneonavicular coalition.  The AP view of the ankle is also used to rule out a valgus ankle.  The most commonly used angles used to evaluate the foot include: calcaneal pitch, talus-first metatarsal ankle on AP and lateral views, and talonavicular coverage.  Advanced imaging is rarely indicated for acquired flexible flatfoot (Bouchard, 2014).


Treatment is indicated in symptomatic patients. Most non-operative interventions have no treatment effect or result in permanent elevation of the arch (Wenger, 1989).  Shoe modifications include a medial heel wedge, arch supports, and orthoses. In addition, a stretching program for tight heel-cords is recommended (Bouchard, 2014, Mosca, 2014).

The indications for surgical treatment include pain and disability that interferes with activities of daily living once non-surgical interventions have been exhausted.  Soft tissue procedures include tendon transfers, soft tissue plications (spring ligament), and isolated Achilles lengthening.  These are rarely successful if performed as isolated procedures in contrast as to when utilized in combination with an osteotomy (Bouchard, 2014).  The arthroresis procedure has been described to restrict subtalar eversion usually by a synthetic, metal, or bone implant placed into the sinus tarsi (Mosca, 2014).  Studies report up to 30% of patients continue with persistent pain and this technique is not recommended (Bouchard, 2014).  Various osteotomies can be employed.  These can involve a calcaneal lengthening osteotomy with or without a medial cuneiform osteotomy.  If there is persistent supination of the forefoot after calcaneus lengthening, some will include medial cuneiform osteotomy.  Alternatively, a calcaneal slide osteotomy in combination with the other aforementioned osteotomies or soft tissue procedures can be employed to achieve the desired outcome of correction (Mosca, 2014).  Finally, an arthrodesis procedure can realign the foot, but reduces mobility and increases risk of developing arthritis in adjacent joints (Mosca, 2014; Skaggs, 2006).


Complications of any surgical procedure can include: infection, wound breakdown due to poor soft tissue handling, persistent pain, and non-union of the graft in osteotomy sites.  Biomaterial problems and inappropriate implantation have been reported in association with subtalar arthroresis procedures (Mosca, 2014).  Subluxation of the calcaneocuboid joint during lateral column lengthening is a well described complication.  Incomplete deformity correction is also a concern.  Failure to address the contracted heel-cord can render the patient in a position of persistent equinus (Mosca, 2014).

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  1. Bouchard, M, Mosca, V. Flatfoot deformity in children and adolescents: Surgical indications and management.  Journal of the American Academy of Orthopaedic Surgery. 2014; 22: 623-632.
  2. Harris RI, Beath T: Army foot survey: An investigation of foot ailments in canadian soldiers. Ottawa, Ontario, National Research Council of Canada, 1947; 1:1-268. 
  3. Joseph, B.  Planovalgus deformity.  In: Paediatric Orthopaedics A System of Decision-Making. London, UK: Hodder Arnold, 2009:44-49.
  4. Mosca, V.  Flexible flat foot in Chapter 29 The Foot. In: Lovell and Winter’s Pediatric Orthopaedics. 7th ed. Philadeplphia, PA: Lippincott Williams and Wilkins, 2014; 1462-1480.
  5. Mosca, V.  Management of the painful adolescent flatfoot. Techniques in Foot and Ankle Surgery. 2014; 13(1): 3-13.
  6. Pfeiffer M, Kotz R, Ledl T, Hauser G, Sluga M. Prevalence of flat foot in preschool-aged children. Pediatrics 2006; 118(2):634-639. 
  7. Skaggs, D, Flynn, J.  Foot problems in children. In: Staying Out of Trouble in Pediatric Orthopaedics.  Philadelphia, PA: Lippincott Williams and Wilkins; 2006: 354-56.
  8. Wenger, DR, Mauldin D, Speck G, et al. Corrective shoes and inserts as treatment for flexible flat-foot in infants and children. Journal of Bone and Joint Surgery Am. 1989; 71(6):800-810.

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