In order to define foot hyperpronation, one must first define foot pronation:
Pronation is a normal rotation that occurs in the feet, in which the subtalar joint (the joint directly underneath the ankle joint) rotates inward, forward and downward as we walk or stand. This inward rotation is such a small amount of movement, that as one looks at the foot (while walking), the rotation cannot be seen.
When the foot normally pronates (technically referred to as Hip Driven Pronation), one will see a well formed inner longitudinal arch in the footprint, similar to the one in Figure A below.
Figure A: This is an example of a foot imprint in the sand. Note the well formed Inner Arch (White Arrow)
It is important for normal foot pronation to occur because this movement allows the entire foot to adapt to uneven ground surfaces (such as stones, slanted or uneven surfaces) when one walks.
Abnormal Pronation (Technically referred to as Gravity Driven Pronation)
Abnormal Pronation (AKA Hyperpronation) is an abnormal (excessive) rotation that occurs in the feet. That is, the inward rotation of the subtalar joint is of such a magnitude that it allows the inner longitudinal arch to move downward towards the ground. If the hyperpronation is severe enough, the inner longitudinal arch may actually reach the ground (See Figure Below).
Figure B: This is an example of a foot imprint in the sand in which the subtalar joint is abnormally pronated. Note the collapse of the inner arch area (flatter foot). This frequently occurs in the PreClinical Clubfoot Deformity.
One can observe the degree of foot pronation by doing a ‘sand or wet foot test’:
- Wet the bottom of your feet and walk on compacted sand or pavement
- Look at the footprints
Normal foot pronation will leave foot imprints similar to the one in Figure A. Excessive foot pronation (hyperpronation) will leave foot imprints similar to the one in Figure B. Please note – In this post, I am talking about the two extremes of foot motion – normal pronation and hyperpronation. However, most people fit in the grey zone. That is, their pronation pattern is neither normal, nor so excessive that their inner arch reaches the ground. In these people (the grey zone- the majority of people), when they are sitting they have a well-formed arch. But when they walk, their arch is lower than when they are sitting, but is not flat. Frequently this can only be observed and recorded by a healthcare provider when they run a gait analysis.