Flat Foot: Causes, Diagnosis and Treatment

Flat foot is a condition characterized by the loss of the normal medial longitudinal arch (curvature of the foot on the inner side behind the great toe) of the foot.

Before reading on it would be good to first understand the anatomy of the foot (skip this if you already done so).

This deformity is of two types

  • congenital (present since birth)
  • acquired

Congenital type is again divided into two types

  • flexible
  • rigid

Flexible type of flat foot with no symptoms is considered to be a variation of the normal foot and requires no treatment.

Flexible type can be differentiated from the rigid type in the following way. In the flexible type the medial longitudinal arch flattens out when the patient stands on his feet and reappears when his feet are off the ground.

In the rigid type the arch is absent whether the feet are on or off the ground.

Causes of the congenital type include

  • tarsal bone coalition (fusion of the tarsal bones normally separated by joints)
  • presence of a extra navicular bone (causes peroneal muscle spasm leading to flat foot)
  • left over deformity after correction of club foot or congenital vertical talus
  • Marfan syndrome and Ehler-Danlos syndrome
  • overall increased ligamentous laxity (loose ligaments)

Causes of the acquired type include

  • weakness of the tibialis posterior muscle
  • fractures of the talus, calcaneum and other bones of the foot
  • dislocations of the foot such as Lisfranc's dislocation
  • rheumatoid arthritis of the foot
  • muscle imbalance in cerebral palsy

Symptoms depend on the cause and include the following

  • can be asymptomatic (no problem is present except that the foot looks flat)
  • pain is present that is increased by standing, walking or running
  • muscle spasm may be present
  • increased mobility of the joints may be seen or there may be stiffness

X rays of the foot can confirm the diagnosis. Abnormal alignment of the bones is seen. CT scan may be required to demonstrate a tarsal coalition.

Treatment of depends on the cause.

Flexible deformity of the foot is treated by a moulded polypropylene orthosis (a plaster mold is taken with the foot in the correct position, this forms a mould for a polypropylene foot support that is then attached to the shoe).

For tarsal coalition

  • use of a firm arch support in your shoe
  • plaster cast (may be required intermittently)
  • excision of bone causing the tarsal coalition
  • fusion of the subtalar, talonavicular or talocalcaneal joints

For extra navicular bone

  • the extra bone is removed surgically
  • and the tibialis posterior tendon that attaches to this bone is tightened

Deformity due to residual club foot or congenital vertical talus and hyper-mobility syndromes are treated by arch supports made of leather, polypropylene or silicone rubber.

Weakness of tibialis posterior requires augmentation by tendon transfer of another muscle to it.

Acquired type of flat foot frequently requires fusion of the subtalar, talonavicular or talocalcaneal joints (called triple arthrodesis).

I hope the information provided was helpful. If you have any query you can ask me at the contact me page.

This page was last updated on 23th June 2009.

Other causes of foot pain...

Hallux Rigidus

Mallet Toe

Hammer Toe




Heel Pain

Sesamoid Fracture

Tarsal Tunnel Syndrome

Talus Fracture

Calcaneus Fracture

Foot Infection

Go back from Flat Foot to Foot Pain


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