What Causes Flat Feet?

There are many different causes of flat feet, which can be separated into two main categories. The first category, congenital flat foot, is a condition that one is born with or is predisposed to at birth. This type includes the completely asymptomatic, pediatric flexible flat foot-by far the most common form of congenital flat foot [2]. Flexible means that an arch is present until weight is put on the foot, at which time the arch disappears. This foot type is a result of the fact that all people are born with different physical features. Some people have bigger noses than others, just as some people have flatter feet (of course, there is no known correlation between the two). Any alteration in the many building blocks of the foot can influence its shape.

At the other end of the spectrum, yet within the same category of congenital flat foot, exist several rare, more severe forms of flat foot. These severe conditions include Vertical Talus, Congenital Calcaneal Valgus, and Tarsal Coalitions-all of which are more rigid (no arch with or without weight on the foot) and definitely symptomatic. Luckily, these are much less common, but can usually be identified by specialists at the time of presentation and treated appropriately.

The second category, acquired flat foot, develops over time, rather than at birth. Many different factors can contribute to the development of flat feet. These include the types of shoes a child wears, a child's sitting or sleeping positions, compensation for other abnormalities further up the leg, or more severe factors such as rupture of ligaments or tendons in the foot. Very commonly, the reason for flat feet is that the foot is compensating for a tight Achilles tendon. If the Achilles tendon is tight, then it causes the foot to point down, or to plantarflex (as occurs when stepping on the accelerator of your car). Even minimal amounts of plantarflexion can simulate a longer leg on that particular side, assuming that the other foot is in the normal position. The body therefore tries to compensate by pronating, or flattening out the arch, thereby making up for the perceived extra length on the affected side.

The most common acquired flat foot in adults is due to Posterior Tibial Tendon Dysfunction [3]. This develops with repetitive stress on the main supporting tendon of the arch over a long period of time. As the body ages, ligaments and muscles can weaken, leaving the job of supporting the arch all to this tendon. The tendon cannot hold all the weight for long, and it gradually gives out, leading to a progressively lower arch. This form of flat foot is often accompanied by pain radiating behind the ankle, consistent with the course of the posterior tibial tendon.

Compounding matters is the fact that the human foot was not originally designed to withstand the types of terrain and forces it is subjected to today. Nowhere in nature do you see the flat hard surfaces that we so commonly walk on in present times. Walking on this type of surface continuously puts unnatural stress on the arch. The fact that the average American is overweight does not help the arch much either-obesity is a leading cause of flat feet as the arch collapses under the excessive bodyweight. Furthermore, the average life span has increased dramatically in the last century, meaning that not only does the arch deal with heavy weight on hard flat ground, but also must now do so for longer periods of time. These are all reasons to take extra care of our feet now in order to prevent problems later.