High Arches vs Flat Feet: Surface Area

As we discussed previously the arch along the inside border of the foot is a dynamic structure, the behaviour of which while weightbearing determines a person’s foot type. Pes planus feet have notably low arches, pes cavus feet have notably high arches, and pes rectus feet sit somewhere in the middle. 

All feet are unique, but these archetypes tend towards certain combinations of factors that can cause foot pain. This is why a lower extremity biomechanical assessment is so important, a pedorthist can determine what specifically, in each case, is causing issues. 

In general, there are three big ways in which foot type can contribute to pain: 

• Surface Area 

• Alignment 

• Shock Absorption 

Let’s take a closer look at surface area today, starting with the image below. Let’s say the people with these different feet and footprints are all the same size and weight, the only real difference between them is their foot type.

A side profile and foot print of a foot with low or fallen arches (left), moderate arches (middle), and high arches (right).

On the left is a pes planus foot and the footprint it leaves. It has a very low arch. In fact, it drops down so much that it is touching the ground. You can’t even really tell that there is an arch there at all. The line from the heel to the base of the big toe is pretty much straight as the arch in this area has collapsed all the way down to the floor. 

In the middle is a pes rectus foot. It’s right in the Goldilocks zone, there is a noticeable arch, but it does drop down a little on weightbearing. The line from the heel to the base of the big toe has a bit of a curve. The entire foot is not flat on the ground. 

On the right is a pes cavus foot, a foot with high arches. Here the arch is so pronounced that not a lot of the middle of the foot is touching the ground at all. All of the person’s weight is focused on the heel, the ball of the foot, and a little strip around the outside edge. 

So, what does all this mean practically? 

Mechanically the more a load is spread out over the same surface area the better it works out for that surface area. In this instance the surface area is your feet. Imagine the difference between being evenly covered in a weighted blanket and having the same weighted blanket balled up and pressing down only on your chest. It is more comfortable to have the weight spread out over a larger area. 

The same is true of your feet. A common complaint amongst folks with high arches is that their heels, the ball of their foot or the outside edge of their foot hurts after they’ve been walking or standing for a while. This can be due to those areas needing to take on all of their body weight while the high part of their arch is way up in the air and not helping out with the load. Instead of, say 90%, of the sole of their foot being in contact with the ground they are only working with maybe 60% and that difference can really add up over a long day on their feet. These areas of high pressure can cause irritation, breakdown of the protective fat pads on the sole of the foot and callus formation.   

In a case like this I would make a set of orthotics that have a relatively high arch. Not because the arch needs any support, it’s supporting itself just fine, but rather to bring the ground up into that empty space to spread the load of their body weight out over a larger surface area. If we increase the overall amount of their foot in contact with the ground, we will be decreasing the peak loading of the areas that are giving them trouble.