An Unstable Foundation

Much of my after school hours and summers of my high school and undergraduate years were spent working construction for my father’s company. Specifically, I worked in concrete construction pouring and framing foundations. Obviously, in the world of concrete, an unstable foundation has disastrous ramifications. Now, as a foot and ankle specialist, I like to believe that I am still in the foundation business, and it still holds true that an unstable foundation has its consequences.

Lateral ankle instability is often the long term consequence of an acute ankle sprain or multiple ankle sprains. It often becomes a vicious cycle as ankle instability subsequently leads to redundant injury. As you may recall from Dr. Abdo’s description of high ankle sprains this past January, the ankle is the most frequently injured joint in athletic competition. Since lateral ankle sprains account for nearly 25% of all musculoskeletal injuries, it comes as no surprise that ensuing lateral ankle instability is relatively common as well.

What is ankle instability and how do we treat and prevent its development? There are two types of instability, mechanical and functional. In order to properly explain each type, a basic understanding of the structures involved is necessary. The ankle is a complex arrangement of tendinous, ligamentous, and boney structures, but to obtain a relative understanding of mechanical and functional instability the lateral ankle ligaments are most important. Three ligaments compose the lateral collateral ligaments of the ankle; the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), and the posterior talofibular ligament (PTFL). The ATFL is the weakest of the three ligaments but also the most important in regards to lateral ankle stability.

Mechanical instability is the actual rupture or stretching of the ligamentous structures, namely the anterior talofibular ligament. This is an objective, clinical finding. This is often determined by a test known as the anterior drawer test. The ability to manually anteriorly translate the ankle is a positive anterior drawer sign.

Functional instability is the subjective presentation of instability. It is the report that the ankle feels like it is going to give out. It is the recurrent instability in sporting activities or every day activities. Functional instability entails what foot and ankle specialists refer to as a proprioceptive defect. Proprioception is the neurological concept of sensing where ones ankle is in space. Functional and mechanical instability often go hand in hand and it is not uncommon to have a patient that embodies both aspects of lateral ankle instability. However, one may have functional instability and not mechanical instability.

Management of lateral ankle instability may occasionally involve surgical reconstruction, but typically always involves a functional rehabilitation program. In essence, the treatment of instability ought to begin with the first acute injury. Less than 10% of patients with an acute injury will ever need surgical stabilization at a later stage in life if initially treated appropriately. Functional rehabilitation or early controlled movement involves a close relationship between the foot and ankle specialist and their local physical therapist.

Lateral ankle instability is, unfortunately common and can have devastating long term consequences. However, a proper understanding of the lateral ankle can assure prompt, appropriate management. Ankle injuries,specifically lateral ankle sprains, will always be prevalent as our population remains active, but instability, on the other hand, does not have too. You have likely heard it said that when one part of the body suffers, the rest suffers as well. This could not be truer with the foot and ankle. When the foundation is not stable, the remaining structure soon collapses.


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