Foot Function & Fascial Lines: Lateral Ankle Stability
In our first article of the Foot Function & Fascial Lines series we explored the integration between the Spiral Line and the Deep Front Line as it relates to propulsion and the 1st MPJ.
In today’s article we are going to explore the functional integration between the Lateral Line and the Deep Front Line – and how understanding this integration can improve rehab and training programs for those clients or athletes with lateral ankle instability.
Importance of Topic
Ankle sprains are one of the most common injuries to the foot and ankle, with a prevalence as high as 70% in sports such as basketball and soccer (Yeung 1994).
Ankle sprains can range from very minor (Grade 1) to so severe the person requires surgery (Grade 3). The most common type of ankle sprain is a Grade 1, or a minor ankle sprain with the most common mechanism of injury as plantarflexion / inversion of the ankle.
According to the American Orthopaedic Foot & Ankle Society, most patients with a minor ankle sprain never seek medical attention – however even the most minor ankle sprains demonstrate residual impairment in stability and proprioception. In fact a 2012 study by Yentes et al. found that those athletes with a history of ankle sprains were at a 5x greater risk of re-injury with 70% of ankle sprains presenting with residual “giving way”.
Dynamic Ankle Stability – An Integrated System
Dynamic ankle stability is achieved through both mechanical structures and neuromuscular control. Both must be present for optimal ankle stability, with the inability of one to make up for the loss of the other.
Mechanical stability comes from ligaments, tendons, bony block and retinaculum (bands of fascia). While neuromuscular stability comes from proprioceptive input from the joint capsule, ligaments, musculotendon junction, fascia and skin.
Although the above structures contribute to dynamic ankle stability on a local level, we must also consider the global control or contribution that more proximal structures have on lateral ankle stability.
Proximal Stability for Distal Mobility
The concept of proximal stability for distal mobility is not new to the health and fitness industry and you may currently look at your clients or athlete assessments and programming with this perspective.
If you have not yet considered the role proximal stability plays in dynamic ankle stability, I challenge you to consider the below concept.
To begin to support this concept of proximal stability for dynamic ankle stability, a 2006 study by Friel et al. demonstrated weaker gluteus medius strength on the same side in subjects with ankle instability.
Does this mean that the ankle sprain led to the gluteus medius weakness? Or vice versa?
Although this may seem like a chicken or egg situation, I strongly believe that it is the latter.
I believe that due to the deep integration between the foot and lumbopelvic hip complex, that a delay in proximal stability would set the client or athlete up for an sprain or ankle instability.
To further explain this concept we must return to Thomas Myers’ Anatomy Trains.
The Lateral Line – A Review
The Lateral Line begins at the base of the 1st metatarsal at the insertion point of the peroneus longus muscle. The peroneus longus travels obliquely across the plantar aspect of the foot, under the cuboid and posterior to the lateral malleolus.
As the peroneus longus travels to the lateral aspect of the cuboid it joins the peroneus brevis muscle which attaches to the base of the 5th metatarsal. Together the peroneus longus and brevus along the lateral aspect of the lower leg to insert at the head of the fibula.
The Lateral Line takes a jump to join the iliotibial band on the lateral aspect of the upper leg and connects to the gluteus maximus and tensor fascia lata. Here the Lateral Line continues to join the internal / external obliques.
The Deep Front Line – A Review
In our first article we described the Deep Front Line, but let’s review again.
In the plantar foot the Deep Front Line consists of the deep posterior leg compartment including the posterior tibialis, flexor hallucis longus and flexor digitorum longus. For the purpose of this article we are going to focus solely on the posterior tibialis.
Running posterior to the medial malleolus and along the medial aspect of the foot, the Posterior Tibialis inserts onto the navicular. After attaching to the navicular the Posterior Tibialis fans out and has 9 osseous and fascial attachments which includes:
– every tarsal bone (except the talus)
– every metatarsal (except the 1st)
– peroneus longus tendon
– flexor hallucis brevis muscle
This fascial attachment between the posterior tibialis and the peroneus longus joins the Deep Front Line to the Lateral Line allowing for more integrated foot biomechanics. So in other words faster dynamic ankle stability (or Lateral Line stability) requires faster stimulation of the Deep Front Line.
Short Foot & the Deep Front Line
So how do we tap into our Deep Front Line faster?
The answer to this question is one of my favorite exercise for foot strength – short foot!
Short foot is a foot activation exercise that was first introduced by Janda et al. This exercise targets the abductor hallucis on the medial side of the foot.
When activated the abductor hallucis does several amazing things:
- abducts the hallux to prepare for sagittal plane push-off
- inverts the subtalar joint creating a locking mechanism in the foot
- supports / lifts the navicular bone to increase the medial arch height
Because the posterior tibialis (Deep Front Line) attaches to the navicular bone, activation of short foot stimulates the Deep Front Line leading to proximal stability and subsequent Lateral Line stability.
The Evidence
A 2009 study by Nigg et al. demonstrated that the greater the intrinsic foot strength the faster the ankle stabilizers fired. Because barefoot training is one of the greatest ways to tap into the foot intrinsics you could argue for the benefit of barefoot training in those clients and athletes with a history of ankle sprains or instability.
A 2002 study by Blackburn et al. demonstrated that after just 7 days of integrated intrinsic foot strengthening (i.e. short foot) gluteus medius activation increased by 200%! This could further support the association between deep foot activation, proximal stability and ankle stability.
Client & Athlete Application
So how do you apply these concepts to your clients and athletes with ankle instability?
First step is teaching them short foot!
After the concept of short foot is understood begin to integrate short foot into all ankle stability exercises. I particularly like barefoot balance exercises with short foot when my patients do their rehab programming.
To see some examples of barefoot balance progressions please click HERE!
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