Pes Planus (Flat Feet): Causes, Symptoms, Diagnosis, Treatment

What is Pes planus?

Pes planus is also known as “Flat foot” is a postural deformity in which your medial longitudinal arch gets collapsed or lowered towards the ground. And the entire sole of the feet touches the ground during standing. The word ‘Pes’ stands for “human foot” and the word ‘planus’ stands for “flat”.

The medial longitudinal arch is elastic and due to its elasticity heavyweights can be supported without any problem. If pes planus deformity develops before or at birth it is known as congenital pes planus. Or if it developed after birth it is known as an acquired pes planus.

Sometimes flat feet can put a lot of strain on your ligaments, muscles, and joints which can lead to a lot of pain in your feet, leg, hips, and back. Treatment is required when flat foot causes pain in the foot or lower limb. Besides treatment, you can consult your doctors and ask for exercises to improve your flat foot conditions.

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Pes planus can be congenital or acquired. It can be unilateral (only one foot is involved) or bilateral (both feet are involved).

Congenital pes planus – The word congenital means that the deformity can be present either at birth or before birth. It can be either unilateral ie present in one foot or it can be bilateral ie present in both the feet.

Acquired pes planus – The word acquired means that the deformity is developed after birth. It can also be either unilateral or bilateral.

What are the causes of pes planus? 

Generally what happens to the medial longitudinal arch from birth up to age 10 years, regarding its development

  • Toddlers of age (1 to 3 yrs) have a fat pad under the medial longitudinal arch which protects the medial longitudinal arch until it develops. Also in this stage, the arch is not visible.
  • Infants of age (4 to 8 yrs) have some arch.
  • A strong normal arch is visible around the age of 10 years.
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Lets us discuss the causes of congenital pes planus and acquired pes planus.

Causes of congenital pes planus-

Laxity –

Normally toddlers of age (1 to 3 yrs) have flat feet, so don’t panic if your child has flat feet. It is because of the

1- Laxity of the Ligament

2 – Abundance of the subcutaneous fat

3 – Lack of neuromuscular control

Absent Arch 

Sometimes from birth, the arch is absent, normally infants of age (4 to 8) are present with some arch but when the arch is absent from the birth infants will show noarch. It happens in very rare cases.

Flexible Flat feet 

It is the most common cause of congenital pes planus in children as there are many flexible flat feet cases. It is a very common finding and almost affects about 10 to 12% of the population. A flexible flat foot will rarely cause pain.

During standing position (weight-bearing), a normal arch will disappear, which should be present. And when you ask your child to tiptoe or dorsiflex the toes, the normal arch will re-appear.


Tarsal coalition 

It is a congenital abnormality. And in this, there is an abnormal fusion between the two tarsal bones which leads to foot pain, multiple ankle sprains, and rigid flat foot in the future.

Generally, after birth, this condition remains asymptomatic and it affects only 5% of the population. Mostly 2 types of the coalition are common Calcaneo-navicular coalition and Talo-calcaneal coalition.


Usually, the coalition is visible around the second decade of life, approx around 10 years those who have Calcaneo-navicular coalition and around 13 to 14 yrs those who have Talo-calcaneal coalition. Because at this age the coalition progresses from fibrous to cartilaginous.

Vertical talus

It is also a congenital deformity in which, from birth, the talus is positioned in the wrong direction. Generally, to get rid out of it surgery is done.


Causes of acquired pes planus-


Both in children’s and women’s, it is seen that obesity is correlated with the development of Flat feet. The extra amount of weight imposes an excess amount of stress on the medial longitudinal arch, which can lead to the collapse of the medial longitudinal arch.

Tightness in Achilles tendon 

The work of the Achilles tendon is to attach the calf muscles to the heel bone(calcaneus). Tightness in the Achilles tendon creates extra stress on the arch, and prolonged stress, on the arch can lead to the collapse of the arch (flat feet)


Posterior tibial tendon Dysfunction 

Posterior tibial tendon Dysfunction (PTTD) is one of the most common causes of adult acquired flat foot. One of the most important tendons in the foot is affected, the posterior tibial tendon.

The function of this tendon(PTTD) is to support the arch as you walk, turn the foot inwards, and to do plantarflexion of the foot. When the posterior tibial tendon gets harmed, swollen, or torn, it can lead to the collapse of the arch.


Women, overweight peoples, rheumatoid arthritis patients, and athletes such as basketball and soccer players are generally affected.

Injury to Plantar fascia 

The work of plantar fascia is to prevent the collapse of the medial longitudinal arch. During toe-off, the toes get dorsiflexed, the plantar fascia is placed under tension.

So Injury to the plantar fascia can also lead to pes planus.

Injury to the Spring Ligaments 

It is an important static stabilizer, it originates on the calcaneus and inserts broadly on the navicular. It acts as a tension band to support the shape of the foot and also acts as a sling to hold up the talar head.


Trauma to midfoot or hindfoot resulting in fractures may increase the risk of developing pes planus.


Some diseases may also increase the risk of developing pes planus.

1 – Cerebral palsy

2-  Obesity

3- Rheumatoid arthritis

4 – Osteoarthritis

5 – Diabetes Mellitus

Pes planus Symptoms 

Difference between Symptomatic Pes planus and Asymptomatic pes planus –

Asymptomatic pes planus 

Pes planus is very common in young infants but it remains painless and asymptomatic (no signs and symptoms) throughout there life. These asymptomatic cases need parent education and no treatment.

Symptomatic pes planus 

Some people who suffer pes planus may show signs and symptoms in any age group. Like

  • In the case of up to 3 years of age group (toddlers) – Chances are very rare.
  • 3-9 years of age group–  Some people will show symptoms,
  • 10-14 years of age group-Usually, pain is present in very rare conditions like in the case of the Tarsal coalition. Some people will show symptoms these patients need treatment.

Tarsal coalition symptoms

In the tarsal coalition when the coalition progresses from fibrous to cartilaginous at age of 12 or 13 yrs.  There will be foot pain, multiple ankle sprains, and rigid or stiff flat foot.

A recurrent ankle sprain is the commonest complaint among individuals who have the tarsal coalition. Because in the tarsal coalition they don’t have a normal subtalar bone. So they do not have that much accommodation to bear the changing forces that comes during walking on the floor or ground which a normal person can easily bear. So they are more prone to get recurrent ankle sprain. and they will suffer pain after these ankle sprain.

Some other common symptoms of pes planus other than a tarsal coalition

Here are some of the symptoms like –

  • Pain in the foot, and particularly in the areas of the heels and arches
  • The pain increases with activity, and the person will get tired easily.
  • There will be swelling along the arches and inside of the ankle.
  • Some people will also suffer hip, knee, and lower back pain due to the abnormal stresses placed on the hip and the knee joints. And their abnormal stresses are also responsible for turning the ankle inward.

Pes planus Diagnosis 

Your doctor will make an objective assessment of your feet by doing a physical examination. This  Objective assessment consists of –

Inspection –

1. Flexible flat foot 

Your doctor will make inspect your feet in both weight-bearing and non-weight bearing positions. Because in the flexible flat foot the normal arch gets disappear in weight-bearing positions and will appear in non-weight bearing positions.

And when you ask your patient to tiptoe or dorsiflex the toes the arch will reappear.

2. Achilles tendon 

Your doctor will ask to perform dorsiflexion and if it is less than 10 degrees then there may be Achilles tendon contracture.

3. Posterior tibial tendon dysfunction 

Your doctor will ask you to perform unsupported heel raises, patients with posterior tibial dysfunction will not able to do this.

Palpation –

Palpation is done for checking swelling and temperature in the painful areas. Your doctor will palpate your posterior tibial tendon and plantar fascia.

Special test and ROM 

There are certain tests that your doctor will perform for checking the flexibility. These tests will help him to differentiate between flexible and rigid flat feet.

  • Jack test
  • Navicular drop test

Gait Assessment 

Your doctor will check your walking pattern which is known as gait pattern for checking the severity of flat foot.

And there are various types of abnormal gait patterns like antalgic gait, ataxic gait, etc. Your doctor will compare your walking pattern(gait pattern) to abnormal gait patterns.

Imaging –


Generally, a normal plain X-ray of the foot will help you in diagnosing the flat foot. Normally flat foot X-ray is done in 3 views anterior-posterior, lateral and oblique. All three views have their specialty in diagnosing flat feet. But the most commonly used view is the lateral view.

The lateral view will help your doctor in finding out the Calcaneonavicular and Talocalcaneal coalition. This view will also help in finding out the Meary’s angle and calcaneal pitch angle which will help in classifying the severity of flat feet.

CT scan

CT scan will help you in determining the size and location of the coalition. As it produces much more detailed and high-quality images of the feet.


MRI can be ordered if in case of any soft tissue injury like if in case of posterior tibial tendon dysfunction, injury to the plantar fascia, or injury to the spring ligament.

Pes Planus Treatment 

Generally, the treatment of pes planus is different in congenital and acquired causes. And it is also based upon symptomatic and asymptomatic cases.

Congenital pes planus Treatment

Flexible flat foot –

A child suffering from flexible pes planus mostly remains asymptomatic and painless. And if the flexible pes planus does not cause any pain, there is no need for the treatment. And sometimes in many cases, the arch may have developed spontaneously as the child reaches 10 years of age.

But in some cases of the flexible flat foot, the child shows symptoms and suffers pain in the medial longitudinal arch and night cramps, These patients need treatment. At first, your doctor will try to manage this conservatively by stretching and muscle strengthening exercises in addition to orthotics.

  • Up to 3 years of age – orthopedic shoes with medial wedges and navicular pads are prescribed.
  • Between 3 to 10 years of age – orthopedic shoes for mild cases and custom-designed arches support insoles for severe cases.

And if conservative treatment fails, and because of pain, the child is not able to perform their daily life activities. then surgery is indicated.

What is Rigid flat foot?

In the rigid flat foot, the arch will be absent either in case of weight-bearing or non-weight bearing. A flat foot generally becomes rigid either in case of vertical talus or when there is an abnormal fusion between the two tarsal bones ie tarsal coalition.

In the rigid flat foot the pain becomes uncontrollable, the patient not able to perform inversion and eversion of the foot.

Vertical talus 

It is a birth defect in which the talus is positioned in the wrong direction. In this case, surgery is performed between 6 months to 2.5 years. The bones are repositioned with the help of pins and casts. After 4 or 5 weeks of the surgery, the pins are removed and a special shoe or brace is prescribed to prevent the reoccurrence.

Tarsal coalition 

It is a congenital deformity in which there is an abnormal fusion between the two tarsal bones. The most important thing about this deformity is that it is often present from birth. But its symptoms are visible around the second decade of life as well as when the person reaches 10 or 13 years of age.

If an asymptomatic tarsal coalition is present, no treatment is required. But when a tarsal coalition becomes symptomatic.

In that case, at first, doctors will go for conservative treatment. like rest, NSAIDs, bracing, arch supports, orthotics. And if the conservative treatment gets fails, and the condition will become severe, then surgery is done for removing the coalition.

In case of Adults and newly acquired flat foot –

Previous Conditions- In adults. if the pes planus has been present form a long time due to flexible flat foot and tarsal coalition. If it is asymptomatic, painless, and not progressing, there is no need for the treatment.

And if in case symptoms arises very late like after 18 years, then at first your doctor will manage it conservatively. And if conservative treatment fails and the case becomes severe then your doctor will go for the surgery.

Newly acquired flat foot- 

In the cases of adults who newly acquired flat foot due to these conditions like

  • Trauma or
  • Posterior tibial dysfunction or
  • Injury to the plantar fascia or due to
  • Secondary diseases like cerebral palsy, osteoarthritis, rheumatoid arthritis, etc.

At first, your doctor will try to find out the proper cause or reason. Then after that, he will first manage the disease conservatively by rest, NSAIDs orthotics, stretching, and strengthening exercises.

And if the conservative treatment fails then your doctor will go for the surgery.

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