Pronation Part VII – How to Address Pronation II – Casting for Orthotics

As mentioned in our last post, many pairs of orthotics are made incorrectly and don’t address the main issue with pronation. Properly made orthotics must have support for the ball of the foot in order to properly address one’s pronation and the issues caused by it. If you haven’t already, go check out our previous pronation posts to get the relevant background information for this post!

Most issues with incorrectly-made orthotics can be traced back to the casting method—i.e., the method used to create the molds of the feet (which are then used to make orthotics). Many methods involve someone stepping into impression molds or onto pressure plates. The problem with this is that the individual is in a weight bearing position, which completely misses the reason behind pronation.

We cannot stress enough that pronation occurs because the ball of the foot must come down to the ground when weight bearing. Therefore, methods requiring someone to be in a weight bearing position will not result in accurate molds of the feet, as they won’t be in a subtalar neutral position. Proper casting methods require people to be in non-weight bearing positions in order to make orthotics properly. That said, many methods involving sitting positions also tend not to result in accurate foot molds: they often rely on active/passive dorsiflexion of the foot to hold the “neutral position” without accounting for the side-to-side rotation that occurs with pronation.

In our clinic, casting is done in a prone (lying face down) position. That way, the feet aren’t loaded and can be properly set (and held) in subtalar neutral while the casts are made. As seen in the video below, strips of plaster are used to encase the feet, which are held in subtalar neutral as the plaster sets. Based off of these molds, the orthotics will then be made with the proper amount of support to keep the ankle in subtalar neutral.

Pronation Part VII – How to address pronation – casting

One last, but very important, thing to remember about orthotics: since pronation is important for shock absorption, orthotics should still allow for some pronation to help with shock absorption, but not so much that the foot is constantly thrown out of neutral alignment.

Pronation Part VI – How to Address Pronation I – Orthotics

When people pronate, they’re often told to strengthen the foot muscles to “build an arch” that sets the foot in a neutral position. However, this assumes that pronation is the same as flat feet, which it is NOT. If you haven’t already, check out our previous pronation posts to get up to speed!

Remember, the issue with pronation is not with the arch, but with forefoot varus when the ankle is in subtalar neutral and the ball of the foot coming down to the ground when weight bearing. Therefore, training the muscles to create an arch helps minimally, as someone with forefoot varus will still pronate when the ball of the foot comes down. Even if the foot muscles can build an arch approximating subtalar neutral and are trained, they cannot maintain it 24-7: muscles eventually fatigue, causing the foot to pronate and the arch to collapse again—when dynamic movement is incorporated, that arch is even more likely to be lost.

So what corrects for pronation? The answer is orthotics: custom insoles made to keep the foot in a subtalar neutral position. This is achieved by supporting both the arch and the ball of the foot, such that it no longer drops when weight bearing—something that cannot be compensated for with foot musculature OR an arch support alone (pronation is a structural issue).

Many orthoses are actually just arch supports, but these don’t help much and may actually make the problem worse! Without support underneath the ball of the foot to maintain the forefoot varus position, pronation still occurs when weight bearing: the foot rolls over the arch support, which can further exacerbate one’s problems. Imagine shoving a rock underneath your foot and walking on it all day!

As seen in the photo, a pronated foot [1] still pronates on an orthotic that’s just arch support [2] because the ball of the foot is unsupported. However, with the properly made orthotics [3], the ball of the foot is supported so the foot no longer pronates and can maintain a subtalar neutral position. That said, there are some (rare) cases of calcaneal or midfoot instability (WITHOUT forefoot varus) that do benefit from arch supports alone. It all depends on the foot structure!

Pronation Part III – Pronation is not the same as flat feet

In our previous post, we discussed what subtalar neutral and forefoot varus are and how they play a key role in determining whether someone pronates—go check it out if you haven’t seen it yet! This post will elaborate on that and focus on the difference between pronation and flat feet.

In the previous post, there is a visible (albeit relatively low) arch when the foot is placed in subtalar neutral. However, that arch disappears when the ball of the foot comes down to the ground and the foot relaxes. Similarly, one could have an arch when the foot is non-weight bearing but becomes flat when weight bearing. In the video below, the foot has a visible arch when lifted off the ground, but again, disappears as soon as it’s lowered and the ball of the foot comes down. Notice how in both anterior and medial views, the lateral (outer) side of the foot hits the ground first—this is indicative of forefoot varus!

Pronation 3_Pronation is not flat feet II

 

Looking at the arch in non-weight bearing positions and weight bearing positions can sometimes offer some insight as to whether you pronate or truly have flat feet. If you have an arch (regardless of how high or low it is) when non-weight bearing but your foot flattens out when weight bearing, then you pronate. And if your foot is flat in both scenarios, then you truly have flat feet. However, the only way to truly tell whether you pronate or flat feet is to put the ankle in subtalar neutral and assess whether there is forefoot varus.

For example, if the ankle is in subtalar neutral and an arch (regardless of height) forms but the person has forefoot varus, then they do not have actually flat feet—they simply pronate. However, if the foot does not exhibit forefoot varus in subtalar neutral and does not create an arch, then the person doesn’t pronated and truly does have flat feet.

 

Key takeaways:

Since the position of the feet in subtalar neutral determines the degree of pronation, the arch collapsing is not the real reason why people pronate. It’s simply an effect due to forefoot varus and therefore, an arch support is not the key to fixing your pronation issues!

Pronation Part II – What is pronation II

Pronation and flat feet are often confused because many pronators have collapsed arches when weight bearing. In other words, when people stand and pronate, their arches often flatten out, which can be misinterpreted as “flat feet.” Before we discuss the difference between the two, we must first discuss the subtalar neutral position of the ankle, and forefoot varus.

When a foot is placed in subtalar neutral, the axis of the tibia, talus, and calcaneus are in line and perpendicular to the ground. In this position, the ankle is neither pronated nor supinated. Once the foot is placed in subtalar neutral, the person’s inherent anatomical structure of the bones determines where the rest of the foot falls. More often than not, when patients are placed in subtalar neutral, the ball of the foot is elevated off the ground (forefoot varus*), as seen in the video. Once that happens, in order to stand and bear weight, the ball of the foot must come down. This is the reason why most people pronate! When the ball of the foot comes down, pronation occurs as the midfoot rotates medially (inward).

Since the degree of pronation is based on how far the ball of the foot comes off the ground when the ankle is put in subtalar neutral (i.e., how far the ball of the foot must come down to reach the ground), people with varying arch heights can still pronate. On the other hand, someone could have anything between high or low arches but not pronate at all. It all depends on where the rest of the foot falls after the ankle is placed into a subtalar neutral position.

 

*Forefoot varus is an angled position of the bones in the forefoot when compared to the heel, where the bones on the inside of the forefoot rest higher than those on an outside, resulting in an oblique angle.

 

Key takeaway:

  • Pronation is not the same as flat feet! It all depends on where your foot naturally positions itself once subtalar neutral is achieved.