High Arches vs Low Arches, What Foot Type Do I Have?

The most commonly discussed arch of the foot is the medial longitudinal arch, a rather wonderfully named bit of anatomy. This is the one that is being referred to when people mention their low or high arches. It is along the ‘inside’ portion of the foot (medial); it stretches from the heel to the ball of the foot making it the longest of the arches in the foot (longitudinal); and is typically arch shaped with the centre elevated higher off the ground than either end (arch). Now, despite being quite descriptive the term medial longitudinal arch is also a bit of a mouthful, so the abbreviation MLA is often used for convenience. 

Most folks will have a relatively prominent MLA when their foot is not weightbearing, for example when you are sitting or lying down. Upon standing up the MLA tends to flatten out. It squishes much like a leaf spring on truck suspension and for much the same purpose, it provides some shock absorption when your foot takes on your entire body weight. Some folks have a stiffer MLA that maintains a very high pronounced arch, and some have a more flexible one that dips down lower when weight bearing. 

This motion, when the arch is dropping down towards the floor, can be referred to as pronation. When the foot is moving like this it is pronating, and when it is in a position like this it is pronated. Conjugation is fun. This is also a mouthful of a technical word so if a foot has a particularly low arch, we call it what it looks like: a flat foot. If we want to be fancy, we call it pes planus, same thing just in something approximating Latin. 

Now, moving in the other direction, when the arch is travelling up away from the floor, such as when weight is being removed from the foot, it is said to be supinating. The motion itself is supination and a foot in this position is supinated. A foot that maintains a substantially raised MLA during weightbearing is a high arched foot. Pes cavus. 

This is... Naturally an oversimplification of pronation and supination which is more-so related to the subtalar joint in the ankle. That will eventually be an entirely different blog post. 

As far as I know there isn’t a widely agreed upon quantitative standard for differentiating between pes planus and pes cavus in regard to vertical arch height (but there is one relating to that subtalar joint). If the MLA is notably low a pedorthist would write pes planus in their notes. Notably high would be pes cavus. If it is somewhere in between, a Goldilocks ‘medium’ arch, I tend to refer to it as pes rectus. Amusingly rectus can mean straight which is a rather silly thing to say about any kind of arch but in the full context of ‘pes rectus’ it reads closer to ‘well aligned foot’ where the lower leg sits nicely and neatly directly on top of the heel. 

Up next some specific thoughts on flat feet and high arches...