Foot Function and Fascial Lines: The 1st MPJ

Fascia.   A term that just a few years ago had little meaning in the performance and fitness industry.   The days of foam rollers collecting dust in the corner have been replaced with courses specializing in fascial dissection, trigger point release and rehab programming related to fascial lines.

As we enter this paradigm shift in the way we look at human movement, corrective exercise and performance I have seen an increase in the appreciation for the foot & the ankle.   With almost every fascial line passing through the bottom of the foot, professionals worldwide can appreciate how integrated the foot and the ankle really is with the rest of the body.

In this article series we are going to take the concept of foot function and fascia further than any course or textbook on the market.  This first article is dedicated to taking a closer look at how the fascial lines influence great toe range of motion.

Let’s take the importance of fascia and foot function one step further and look at propulsion!

Propulsive Phase of Gait

Big toe

Whether we are walking, running or jumping – push-off or propulsion is characterized by dorsiflexion of our digits at the metatarsophalangeal joint (MPJ).   The joint that takes a majority of the forces during push-off and is responsible for the release of elastic energy is the 1st MPJ.

As much as dorsiflexion of the 1st MPJ may seem like a simple biomechanical movement, it is actually quite complex – requiring timed control and activation of our fascial slings.

Let’s take a closer look at the 1st MPJ.

The First Metatarsophalangeal Joint


The 1st MPJ is formed by the base of the proximal phalynx and the head of the 1st metatarsal.   Sitting directly under the head of the 1st metatarsal and lying within the tendons of the flexor hallucis brevis are the sesamoids.   Inserting on the medial aspect of the proximal phalynx is the abductor hallucis which is opposed laterally by the adductor hallucis.

As we begin to transition onto the forefoot and into propulsion, what dictates the range of motion of the 1st MPJ is first metatarsal position in the sagittal plane.     The image below illustrates how an elevation of the first metatarsal in the sagittal plane can block the dorsiflexion or gliding the proximal phalynx over the head of the first metatarsal.


So what dictates the position of the first metatarsal in the sagittal plane thereby playing a role in 1st MPJ dorsiflexion at propulsion?

If you guess the Spiral Line you are correct!

The Spiral Line – Expanded Version

In Thomas Myers’ Anatomy Trains he describes the lower part of the Spiral Line as the tibialis anterior as it joins the peroneus longus at the level of the base of the 1st metatarsal.


Often referred by Myers at the “stirrup” of the foot, I want to expand upon this concept a little further and demonstrate how the Spiral Line plays a bigger role in propulsion than you may think!

The tibialis anterior muscle runs down the anterior aspect of the lower leg to insert on the medial aspect of the foot on the medial cuneiform (90%) and the base of the 1st metatarsal (10%).   Joining plantarly is the peroneus longus tendon which runs along the lateral aspect of the lower leg, behind the lateral malleolus and under the cuboid to insert on the base of the 1st metatarsal (90%) and medial cuneiform (10%).

With 90% of it’s insertion on the base of the 1st metatarsal, the peroneus longus plays an important role in plantarflexion of the 1st metatarsal allowing dorsiflexion of the 1st MPJ during propulsion.

So does this mean that for optimal propulsion and dorsiflexion of the 1st MPJ all we need to do is ensure proper activation of the peroneus longus muscle or the Spiral Line?

Unfortunately it isn’t that easy!   Proper activation of the Spiral Line is actually integrated with another fascial line – the Deep Frontal Line.

The Deep Front Line

For the Deep Front Line again we return to Myers Anatomy Trains.

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 soley 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

Anatomy Foot

This fascial attachment between the posterior tibialis and the peroneus longus joins the Deep Front Line to the Spiral Line allowing for more integrated foot biomechanics.

EMG studies have shown that the posterior tibiailis activates prior to the peroneus longs during the gait cycle which means this fascial integration between the PT and PL prepares the foot for propulsion.

With the posterior tibialis as a driver of subtalar joint supination or inversion just prior to heel lift, a reflexive activation of the Spiral Line leads to stabilization of the 1st metatarsal by the peroneus longs –  allowing for dorsiflexion of the 1st MPJ and propulsion.

Client & Athlete Application

When assessing optimal propulsion in our clients and athletes remember the function of the Spiral Line and Deep Front Line on 1st MPJ dorsiflexion.   A limitation in 1st MPJ dorsiflexion or power at propulsion may be related to an impairment in posterior tibialis strength.

To optimize posterior tibialis strength in clients and athletes integrate barefoot exercises such as short foot which picks up the navicular bone and stimulates the Deep Front Line.   In addition single leg exercises can used the strength the posterior tibialis and it’s co-activation patterns with the gluteus medius and maximus.

Take a look at our webinar for related information: Optimizing Power at Push Off | High Gear vs Low Gear Position with Dr Emily Splichal

To learn more about about foot function and barefoot strengthening please visit:

Are you barefoot strong? 


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