Flatfoot is defined as a lack of the medial longitudinal arch of the foot. Adults with flat feet demonstrate several biomechanical inefficiencies in the foot and ankle, as well as a variety of gait abnormalities. The development of clinical problems is dependent on the levels of activity and the amount of repetitive stress the feet must endure. The average person spends four hours each day on their feet, and takes between 8,000 and 10,000 steps every day. In some jobs and many sports, these amounts are more than doubled. During an average day, the feet support a combined force equivalent to several hundred tons. In addition to carrying the weight of the body, each foot acts as a shock absorber and a lever to propel the leg and body forward, and it serves to balance and adjust the body to uneven surfaces. The various problems associated with flatfoot can interfere significantly with normal daily activities, as well as limiting participation in recreational and competitive sports. Flat feet are due to either a loss of the normal arch due to breakdown of the supportive collagen structures, or a lack of development of a normal arch in the first place.
Until about the age of 2 years, infants have flat feet, due to the presence of a large medial fat pad, and incomplete development of the foot structures. (1) As children begin to walk and spend more time on their feet, this fat pad slowly decreases, resulting in a noticeable medial longitudinal arch. (2) A study of the developing arch in children has confirmed that 28 to 35% of school children have an apparent flatfoot deformity, but 80% of those are classified as “mild.” (3) Follow-up evaluations have determined that 90% of these children will have normal arches by the age of 10 years. (4) The remainder never develop an arch, and are considered to have a “congenital flatfoot.”
As adults, some of those who did develop a normal arch gradually lose it. This occurs secondary to a breakdown of the normally strong and dense connective tissues of the foot. It is the ligaments and connective tissues that support the medial longitudinal arch, (5) and not muscular strength. (6) In fact, normal alignment depends on a complex arrangement of dense collagenous fibers, and no single structure provides all of the support. (7) Problems with this arch will develop when these supportive tissues are put under excessive stress. This can be either from high loads for sudden, brief periods, or from more moderate, but repetitive stresses over longer periods, resulting in an “acquired flatfoot.”
The overwhelming majority of flat feet are considered “flexible,” and will respond well to external support. In some cases, however, the arch never develops due to a bony abnormality (most commonly a tarsal coalition). This results in a “rigid” flatfoot, which will can be greatly aggravated by attempts to provide external support with inserts and orthotics. Differentiation is important, but can be easily done during the examination. If an arch is present when the patient is sitting with the foot dangling, or when standing up on the toes (toe-raise test), then the flatfoot is “supple and is correctable with an arch support.” (8) If the foot remains flat and rigid during this test, any attempt to lift up or support the arch can be painful, and corrective orthotics generally are avoided. Evaluation by a foot specialist is usually necessary to determine the underlying cause of a rigid flatfoot. Treatment may consist of accommodative orthotics and/or surgery.
Two descriptive terms are often used interchangeably with flatfoot, and can contribute to confusion. Pes planus is the more technical term that represents a flattening of the longitudinal arch; the arch is lower than established normal parameters when standing, especially on radiographic evaluation. (9) Hyperpronation (or excessive pronation) refers to excessive medial deviation of the talus during gait, primarily during the stance phase of gait. (10) Both of these problems are found in patients with flexible flatfoot, and will interfere with lower extremity biomechanics. An extensive list of the varied symptom complexes and health problems caused by flexible flatfeet has been compiled by Dr. Yale (Table 1). (11)
Energy Cost / Athletic Performance
An interesting study assessed the effects of arch supports on oxygen consumption in 20 subjects with flat feet who complained of fatigue and “weariness.” (12) The participants were between 18 and 38 years old, and had no specific foot symptoms. Their heart rates, blood pressures, and walking oxygen consumption were measured on a treadmill – first without, and then with arch-supporting orthotics. The results demonstrated that use of the orthotics significantly improved their gait efficiency, and decreased their oxygen consumption during normal walking. These responses can be extrapolated to athletic performance. In fact, it has long been observed that a flat foot, and hyperpronation, in particular, can interfere with performance in a number of sports. (13)
Support From Orthotics
In order to improve the biomechanics of the foot and provide permanent support for the medial longitudinal arch, most patients will need custom-fitted orthotics. Active patients generally benefit from flexible orthotics which are most beneficial for athletes and workers who must be on their feet for many hours each day. A recently published study found that custom-made flexible orthotics cast in a weight-bearing position significantly improved the alignment of the foot and increased the medial longitudinal arch when standing. (14) The materials and fit of an orthotic are critical, since support is needed for all three arches of the foot, along with cushioning and shock absorption in a comfortable insert. Additional padding under the forefoot is a recent addition that appears to be very helpful.
Flatfoot in adults may be congenital (the medial arch never developed), or acquired (the connective tissues no longer can support the medial arch). A rigid flatfoot is due to an osseous deformity, such as a tarsal coalition. As long as a flat foot is flexible, orthotic support for the medial arch can improve foot and ankle biomechanics, decreasing hyperpronation and enhancing performance in daily activities and during sports.
1. Magee DJ. Orthopedic Physical Assessment. Philadelphia: WB Saunders; 1987, 329.
2. Kemp HC. Current Pediatric Diagnosis and Treatment. Norwalk: Appleton and Lange; 1984, 614.
3. Notari MA. A study of the incidence of pedal pathology in children. J Am Podiatr Med Assn 1988; 78:518-521.
4. Wetton EA. The Harris and Beath footprint: interpretation and clinical value. Foot & Ankle 1992; 13:462-468.
5. Huang CK, et al. Biomechanical evaluation of longitudinal arch stability. Foot & Ankle 1993; 14:353-357.
6. Basmajian JV, Stecko G. The role of muscles in arch support of the foot. J Bone Joint Surg 1963; 45A:1184-1190.
7. Kitaoka HB, et al. Stability of the arch of the foot. Foot & Ankle 1997; 18:644-648.
8. Hoppenfeld S. Physical Examination of the Spine and Extremities. New York: Appleton-Century-Crofts; 1976, 232.
9. Forrester D, Kerr R, Kricun ME. Imaging of the Foot and Ankle. Gaithersburg: Aspen Pubs; 1988.
10. Gould N. Evaluation of hyperpronation and pes planus in adults. Clin Orthop Rel Res 1983; 181:37-45.
11. Yale JF. The conservative treatment of adult flexible flatfoot. Clin Pod Med and Surg 1989; 6:555-660.
12. Otman S, et al. Energy cost of walking with flat feet. Prosthets and Orthots Intl 1988; 12:73-76.
13. Subotnick SI. Sports Medicine of the Lower Extremity. New York: Churchill Livingstone; 1989, 159.
14. Kuhn DR, et al. Radiographic evaluation of weight-bearing orthotics and their effect on flexible pes planus. J Manip Physiol Ther 1999; 22:221-226.
Table 1. Flexible Flatfoot Associated Pathology (11)
- Medial longitudinal arch strain with pain in the spring ligament
- Abductor hallucis strain, pain, and spasm
- Plantar fascial inflammation
- “Jamming” at the first metatarsophalangeal joint with resultant traumatic arthritic changes
- Plantar fascial insertional strain and inflammation, with or without calcaneal exostosis (heel spur)
- Periarticular fibrocystis of the second metatarsophalangeal joint (Morton’s syndrome)
- “Pinching” of the calcaneofibular ligament
- Secondary fifth toe contraction deformities
- Shearing hyperkeratotic lesions beneath the metatarsal heads
- Second or third intermetatarsal space neuritis or neuroma
- Sinus tarsi syndrome
- Achilles tendinitis
- Anterior or posterior Achilles bursitis
- Peroneus longus spasm
- Tibialis posterior overuse (posterior shin splints)
- Tibialis anterior overuse (anterior shin splints)
- Patellar tendinitis
- Medial collateral knee ligamentous strain
- Patellofemoral syndrome
- Synovial plica syndrome
- Popliteus muscle syndrome
- Iliotibial band syndrome at knee or hip level
- Hip adductor tendinitis
- Greater trochanteric bursitis
- Hamstring muscle strain and spasms (usually at night)
- Lumbosacral muscle spasms
- Sciatic neuritis
- L4, L5, S1 disc narrowing symptoms
- Cervical muscle spasm
- Temporomandibular joint syndrome