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April

The Unintended Consequences of Limiting Pronation

Lately we have seen an increase in the amount of anterior ankle impingement in runners, so I thought I’d make a post about it.

First, the patient’s version, and if you’re really interested, the clinician’s version is further down the page.

Patient’s Version

Dorsiflexion is the closing in of the angle between the front of your shin and the top of your foot. It is what happens when the knee travels forward over the foot during running, squatting, or getting up out of a chair. Many people have limited range of motion for dorsiflexion.

There are several strategies to compensate for this while running: shortening your stride length, lifting the heel early or reducing the amount that your knee bends. There is also a key strategy in the foot and that is to increase the amount of bending within the foot (called midfoot dorsiflexion). The only way to achieve more of this is by pronating the foot (allowing the inside ankle bone to roll inward)

To prove this is easy – simply do the two different calf stretches shown in the diagram below. You will find that your knee can travel forward further when the foot is allowed to pronate.

If you are told that you “overpronate”, you need to consider WHY you were told this (you can read my take on “overpronation” here). There are many reasons why people are told this. Some are legitimate, some are questionable. Here is one example: Are you pronating a lot to compensate for limited dorsiflexion in the ankle? If you are, and you make attempts to limit this compensatory motion, you are now placing more of a burden on the dorsiflexion at the ankle. This may place you at greater risk of injury.

In my office, I see quite a few people who suffer from “anterior ankle impingement” and it is often because they have stiff, inflexible joints in the midfoot and also we see it in runners who have been limiting the pronation in the foot via over-the-counter pronation control footbeds and/or pronation control shoes.

Find the cause and fix it.

Clinicians Version

The total amount of forward tipping angle that the tibia achieves over the foot during dorsiflexion (DF) is derived mainly from two components: the DF at the ankle joint and the DF from the foot. It is thought that the majority of DF in the foot comes from the midtarsals (calcaneocuboid and talonavicular), but there is also contribution from the tarsometatarsal joints. Running gait requires approx. 20 degrees of ankle DF which is significantly more than with walking [Dugan et al., 2005]

Unfortunately, it is common to find a restricted amount of ankle DF in many patients. During the gait cycle, people can compensate for limited ankle DF for in many ways. From a proximal compensation, runners can shorten their step length, have an early heel rise, or reduce their knee flexion. It can also be compensated for more distally by increasing pronation in order to allow more DF in the midfoot [Johanson et al., 2008]. This is because the midfoot is relatively immobile when the subtalar joint (STJ) is supinated, but increasingly more mobile as the STJ is pronated [Karas et al., 2002]. Pronation of the STJ allows the midtarsal joint axes (talonavicular and calcaneocuboid) to become parallel, which increases mobility [Dugan et al., 2005]

This short 1 minute video helps explain:

This is important to consider, so I will repeat….Midfoot motion is dependent upon STJ pronation. Without STJ pronation, very little dorsiflexion from the midtarsals can be achieved. [Karas et al., 2002].

Why do we care about all that?

When runners go and purchase shoes, they are usually evaluated for pronation (You can read my take of “overpronation” here). If they are deemed to pronate too much, they are put in OTC footbeds and/or shoes designed to reduce pronation. If they are put in the dreaded “overpronation” category, are they ever evaluated as to WHY they are overpronating? There are many reasons why people pronate, but I have listed just one of them in this post: to help achieve adequate dorsiflexion.

If they have some amount of ankle equinus and they are relying on midfoot motion to attain suitable dorsiflexion, why would you attempt to stop that? Why not fix the origin (in this case, reduced talocrural dorsiflexion)? But very few people are checking for the “reason” there is excessive pronation.

Lately, my office has seen a surge of anterior ankle impingement cases, resulting in cartilage degeneration and tibiotalar osteophytes. Too often, there has been some pronation control device behind the scenes, limiting STJ pronation and thus limiting midfoot dorsiflexion which inevitably results in increased reliance on ankle dorsiflexion and tibiotalar impaction.

Find the cause and fix it

- Kevin Maggs, ,

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