Pes Planus

Article Author:
Marc Raj
Article Author (Archived):
Alexei DeCastro
Article Editor:
John Kiel
6/28/2019 10:27:58 PM
PubMed Link:
Pes Planus


Pes planus, commonly referred to as “flat feet,” is a relatively common foot deformity. Specifically, it refers to the loss of the medial longitudinal arch of the foot where it contacts or nearly contacts the ground. The arch of the foot is a tough, elastic connection of ligaments, tendons, and fascia between the forefoot and the hindfoot. It serves as an adaptive support base for the entire body. It functions to dissipate the forces of weight bearing and acts to store energy during the gait cycle. Dysfunction of the arch complex is usually asymptomatic, but it can alter the biomechanics of the lower limbs and lumbar spine causing an increased risk of pain and injury.[1][2]


Pes planus can either be congenital or acquired.[3][4][5]


Pes planus is fairly common in infants. Infants and young children are prone to absent arches secondary to ligamentous laxity and lack of neuromuscular control. Infants have a fat pad under the medial longitudinal arch which serves to protect the arch during early childhood. Most children develop normal arches by age 5 or 6. Most cases of pes planus in children are flexible. Flexible pes planus describes a normal arch without bearing weight which disappears with weight bearing. There is a small percentage of children who fail to develop a normal arch by adulthood.  Obesity in children is significantly correlated with the tendency of the longitudinal arch to collapse in early childhood.


Acquired pes planus is most commonly occurs secondary to posterior tibial tendon dysfunction. The function of the posterior tibial tendon is to support the arch as well as inversion and plantarflexion of the foot. It is most common in females over the age of 40 with comorbidities including diabetes and obesity. It can also occur in adults with congenital pes planus especially those who participate in repetitive high impact sports such as basketball, running, or soccer.

Patient with trauma to the midfoot or hindfoot resulting in navicular, first metatarsal, calcaneal, or Lis Franc fractures increase risk of developing pes planus. It occurs more commonly in malunion of those fractures. Other causes include injuries to the soft tissues such as plantar fascia or spring ligament. Patients with sensory neuropathy may result in Charcot arthropathy leading to midfoot collapse over time.

Patient’s with congenital ligamentous laxity secondary to Down syndrome, Marfan or Ehlers Danos are uncommon causes. Ligamentous laxity secondary to pregnancy may also cause pes planus, but typically corrects itself post-partum.

Patients with arthropathies are at higher risk for acquired pes planus. These can be either degenerative or inflammatory. Patient with rheumatoid arthritis or seronegative arthropathies should be considered at higher risk for developing pes planus especially if poorly controlled.

Rigid pes planus is rare. It usually develops during childhood, but it can occur at any point in life. It develops from the tarsal coalition, accessory navicular bone, congenital vertical talus, or other forms of congenital hindfoot pathology.


It is estimated that about 20% to 30% of the population has some degree of pes planus. A majority of these cases are flexible pes planus. A 2003 study by Dunn et al. found that the prevalence among non-Hispanic whites was 17% and greater among Africa Americans at a rate of 34%. There is a 1:1 ratio of men to women. It is typically more common in children, but most children develop a normal arch by the age of 10. There is a strong genetic component of pes planus, and it typically runs in families. The radiographic or clinical presence of pes planus may be an incidental finding in patients and requires clinical correlation.[6][7][8]


The medial longitudinal arch is made up of the calcaneus, navicular, talus, first three cuneiforms, and first, second, and third metatarsals. It is supported by the soft tissues of the spring ligament (plantar calcanea navicular ligament), deltoid ligament, posterior tibial tendon, plantar aponeurosis, and flexor hallucis longus and brevis muscles. Dysfunction of any portion of the medial longitudinal arch may result in acquired pes planus. The main factors that contribute to an acquired flat foot deformity are excessive tension in the triceps surae, obesity, posterior tibial tendon dysfunction, or ligamentous laxity in the spring ligament, plantar fascia, or other supporting plantar ligaments. It may also result from a tight Achilles tendon or calf muscle.

Rigid pes planus is rare. It usually develops during childhood, but it can occur at any point in life. It develops from the tarsal coalition, accessory navicular bone, congenital vertical talus, or other forms of congenital hindfoot pathology.

History and Physical


Evaluation should be based on presentation. Pes planus is very common in young children and asymptomatic. In rare instances, flat feet can become painful or rigid, which may be a sign of underlying foot pathology, such as tarsal coalition. Through developmental history, past medical history, past surgical history, family history of pes planus, and activity level (sports participation or avoidance) should be documented.

In adults, pes planus may be an incidental finding. In symptomatic patients, there may be complaints of midfoot, heel, lower leg, knee, hip, and or back pain. Patients with more advanced changes may complain of altered gait pattern. Patient’s who typically over pronate will be at high risk for ankle sprains from chronic “rolling of the ankle.” The patient should be asked about the onset of deformity, timing of symptoms, severity of past and current symptoms, history of trauma, family history, surgical history, and past medical history (including HTN, diabetes, Rheumatoid arthritis, sensory neuropathies, seronegative spondyloarthropathies, and obesity).

Physical Exam

The physical exam should consist mainly of inspection, palpation, ROM, muscle strength testing, and gait assessment. Comparison should be made to the unaffected foot.

Inspection: The Examiner should evaluate the patient with and without weight bearing. The flat foot should be apparent on inspection. The flexible flat foot will have an arch without weight bearing which will disappear with weight bearing. The patient will be noted to overpronate. Looking at the patient from the back will show the “too many toes” sign. Both feet should be compared for asymmetry.

Palpation: Examiner should palpate the posterior tibial tendon, lateral rearfoot, and plantar fascia.

ROM:  This will differentiate flexible versus rigid pes planus. Flexibility can also be assessed by using the Hubscher maneuver (Jack test) to determine if the deformity is reducible.

Muscle strength testing:  Examiner can evaluate muscle strength by having the patient perform single toe raise. Posterior tibial tendon muscle strength can be evaluated by having the patient invert the foot against resistance.

Gait assessment: Patient may have antalgic gait. Examiner may notice overpronation with ambulation.



Routine radiographs may include standing anterior-posterior (AP), dorsoplantar which shows the degree of heel valgus (talocalcaneal angle), lateral and oblique views, as well as Harris-Beath views if a tarsal coalition is suspected.

MRI Foot and Ankle

MRI can be performed if posterior tibial tendon dysfunction or injury to the spring ligament or other supporting soft tissue structures is suspected.


EMG and nerve conduction studies can be performed to evaluate for sensory neuropathy.

Treatment / Management


Children rarely require treatment for pes planus. Foot orthotics are indicated for foot pain secondary to pes planus alone or combination with leg, knee, and back pain. Surgery is only indicated for rigid pes planus.


In adults, treatment is based on etiology. Foot orthotics and NSAIDS are sufficient for pain. The patient should be counseled on proper footwear. Patients with pes planus could benefit from motion control shoes. Obese patients should be counseled to lose weight through diet and exercise. For posterior tibial dysfunction, treatment initially consists of rest, NSAIDs, and orthotics. Surgery is reserved for cases resistant to therapy.

Pearls and Other Issues

  • Pes planus is a common finding on clinical exam and may an incidental finding patient. It can be aquired or congenital
  • Treatment is typically non-surgical and requires modification of footwear and orthotics

Enhancing Healthcare Team Outcomes

Pes Planus is best managed by an interprofessional team that also includes orthopedic nurses and therapists. Clinicians should be fully aware that Children rarely require treatment for pes planus. Foot orthotics are indicated for foot pain secondary to pes planus alone or combination with leg, knee, and back pain. Surgery is only indicated for rigid pes planus. In fact, unnecessary surgery in children can lead to more harm than good. In adults, surgery may be an option for pes planus but overall the results are not satisfactory. Most patients have decent outcomes with the use of orthotics.


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