Flat feet or pes planus or pes planovalgus can be quite an annoying and disabling condition until and unless intervened into it. Here are 15 steps to comprehensive understanding of flat feet.

1. Introduction:

Flatfoot or pes planus is a condition in which arches of the feet (both longitudinal and transverse) are not formed properly or these are absent. This malformation of the arches results in flat feet, which are expressed as entire plantar aspect of the foot touching down on the ground, while weight bearing. Adult flatfoot is the condition that is present after skeletal maturity and needs treatment, while constitutional flat foot is a congenital, non-pathological condition seen in children hence does not require treatment.

2. Etiology:

There are many underlying etiologies of a flatfoot, which include fracture of bones of foot, dislocation of small joints of foot, arthritis affecting the foot, neuropathy with neuropathic joints, neurologic weakness of the supporting muscles and iatrogenic flatfoot. However most common cause remains the posterior tibial tendon dysfunction.

3. Pathology:

All the structures in the feet are interconnected, interwoven and functionally interdependent. If one of the components malfunctions it leads to impaired function of all the other structures and consequently that of the entire foot.

The components of the feet include muscles, ligaments, tendons and bones.

4. Muscles:

There are short and long muscles affecting the dynamics of the feet. The long muscles are the ones that run down from leg across ankle and insert into foot. These long muscles are very good stabilizers and movers of the foot and there misalignment and malfunction is the main contributor towards the formation of flat feet. Small muscles of the feet are arranged in 4 layers in the plantar aspect of the feet. These mostly act as cushion while weight bearing and keep the toes well aligned.

5. Ligaments:

Ligaments are the supporting structures of the joints. These are made up of collagen fibers and connect different bones of the foot with each other to form joints. The major group of ligaments whose dysfunction causes flatfoot are spring ligaments that support the talonavicular joint. These ligaments along with posterior tibial tendon and plantar fascia support the medial arch of the foot, which is a major contributor towards normal shape of the foot.

Any injury, congenital laxity or any other damage to these ligaments compromises a major support for the joints of the foot and consequently integrity of the arches of the foot leading to formation of flatfoot.

6. Tendons:

Tendons are the structures that connect muscles to the bones. These are made up of collagen fibers and are an important component of the support system of the foot. One single tendon that can precipitate flatfoot due to its dysfunction is posterior tibial tendon. Its misalignment and dysfunction leads to collapse of longitudinal arch of the foot leading to formation of flatfoot.

7. Bones:

Bones also contribute towards development of flatfoot. Underlying bony cause can be either congenital or acquired. An important example of congenital cause is tarsal coalition, which means two or more conjoined tarsal bones. Most commonly calcaneus and talus or calcaneus and navicular are conjoined together.

There can be various acquired causes however most common is trauma, which causes fractures leading to deformation of bones and consequently collapsed arches and hence flatfoot.

Another important cause can be neuroarthropathy (Charcot foot), which most commonly occurs in diabetics. Strict blood glucose control is required to avert its development.

8. Features:

Most common presenting feature of flatfoot is pain. Pain due to flatfoot can affect various parts of the body as entire kinetic chain is affected by flatfoot. Pain starts at foot most commonly from heel and arch area and gradually involves knee and back too.

Another feature is swelling at the medial (inner) aspect of the ankle. With further advancement it leads to development of arch strain.

9. Assessment:

There are a few clinical and radiological tests to confirm diagnosis and type of flatfoot.

A. Wet Footprint Test:

First of all a wet footprint is acquired by soaking the foot in the water and then placing it on a cardboard or a paper while full weight bearing. A flatfoot will leave a complete print of the sole while a print of the normal foot will have missing inner border/ instep of the foot.

B. Toe Standing for Flatfoot:

Toe-standing  is a clinical test where patient is asked to stand on toes, if an arch forms by doing so in an otherwise flatfoot then it is labelled as a flexible flatfoot. If no arch forms then it is labelled as rigid flatfoot. In case of painful toe-standing further tests are warranted.

C.  Abnormal Wear & Tear Pattern of Sole of The Shoe:

Abnormal pattern of wear and tear of the shoe heel and medial border of its sole can be observed.

D. Too Many Toes Sign:

When viewed from behind, 1 or 2 toes are visible in normal subjects. If 3 or 4 toes can be seen from behind it means there is abnormal heel valgus and forefoot abduction. This increased number of visible toes from behind the flatfoot subject is known as too-many-toes sign.

E. Computed Tomography (CT):

CT scan is carried out to find out the integrity and congruence of bones of foot.

F. Magnetic Resonance Imaging (MRI):

MRI will show the soft tissues such as tendons and ligaments in detail.

G. Plain X-Ray:

X-ray of the foot is very useful in determining the extent of the collapse of arches and serial X-rays determine improvement or deterioration in the condition. Standard anteroposterior and lateral views of the foot are obtained.

Lateral view of the flatfoot will reveal sagging arch at naviculocuneiform or talonavicular joint. This sagging arch leads to decreased calcaneal pitch (normal value is 20-25 degrees), decreased lateral first talometatarsal angle and reduction in height of the medial cuneiform. All these changes are visible on lateral radiograph.

The anteroposterior radiograph of a flatfoot will show increased talonavicular angle, which is caused by lateral subluxation of the talonavicular joint.