Link to Part one of the Series:
https://mewithlauriebb.com/plantar-fasciitis-part-one/
Part 2 describes what the plantar fascia does during the gait cycle.I’ve tried to keep it simple, but sadly that’s not necessarily my forte, and this part of understanding plantar fascia function can be a little dense.
Why is it important?
What the plantar fascia does or doesn’t do may play a huge role in why we end up with plantar fasciitis, but more importantly what we might do to prehab and/or rehab this vital area of our body.
Part 3 will address “itis” versus “osis”, prognosis, and what evidence based practice says about managing PF once its shown up.
Plantar Fascia and Gait
The plantar fascia has a dynamic function during gait.
Remember that the plantar fascia connects the heel to all 5 toes on the bottom of your foot.
As you move your foot to the ground during gait, the plantar fascia has to continuously change its shape/tension against the load of your body and that of ground force reaction (the force exerted by the ground/surface you are walking on against the foot) (Kaliniev et al., 2013).
Stance Phase of Gait
When your heel strikes the ground the ankle is in dorsiflexion (top of the foot pulled back towards your shin), at the beginning of what is called the stance phase of gait.
Your foot is in the preparatory phase of allowing you to eventually stand on it so the other foot can swing through.
As that heel bears weight and the foot begins to move towards the ground, a variety of joints in your ankle and foot change their position, creating a pre-loading effect on your plantar fascia.
Elongated tension is created in the plantar fascia because it’s getting ready to allow you to stand on the foot and then help to push that foot forward off the ground.
Mid-Stance of Gait
When the foot reaches what is called mid-stance (you are now standing more or less on one leg over that foot) the tension in the plantar fascia decreases so the foot can shock absorb and adapt to the terrain you’re standing on.
Terrain includes not only the type of ground you are on – concrete, sand, dirt trails – but also the type of shoe you are wearing.
Depending on your habitual movement patterns, the type of terrain you’re on, and what kind of action you’re taking (walking versus running), the various joints in the foot and ankle will respond, so the arch has to be able to change shape and adapt.
If the plantar fascia tension did not decrease, the arch would not be able to change, adapt, and shock absorb.
Late Stance of Gait and the Windlass Mechanism
In the last 30% of the stance phase of gait you are getting ready to push off and swing that foot forward for the next step.
It’s here that an action named the Windlass Mechanism occurs.
The word “windlass” explains the action of hauling or tightening something with a cable or rope (Bolgla & Malone, 2004).
In gait, push off requires the toes, but especially the big toe to bend, or dorsiflex (see the above photo and look at the bend of the big toe).
This toe dorsiflexion winds the plantar fascia around the head of the metatarsals, the long bones that articulate with each toe, changing the tension in the plantar fascia (Bolgla & Malone, 2004).
The plantar fascia acts as a cable to shorten the distance between the big toe and the heel, which raises the medial longitudinal arch (Carravagi et al., 2009). This shortening due to big toe dorsiflexion is the essence of the windlass mechanism.
This schematic allows you to see the mechanics of the Windlass mechanism. The base of the triangle is the plantar fascia (plantar aponeurosis). Figure B presents the difference in plantar fascia length while flat footed versus activated big toe dorsiflexion, and how the medial longitudinal arch is raised in response.
The windlass mechanism helps to maintain the arch so that we can move in a more efficient manner. It helps to “stiffen” the foot and store elastic energy so that you can push that foot off the ground, swing it forward, and start the whole thing over again.
Although the plantar fascia plays a number of roles in foot function, the main role is to maintain the arch throughout gait and contribute to the windlass mechanism (Carravagi et al., 2009).
Try this:
While standing, reach down and lift your big toe up.
Can you see your arch lift? Can you see how your big toe moves closer to your heel?
Now while standing roll your heel off the ground until you are on the ball of your foot. Your toes are now “extended” or dorsiflexed.
Can you sense how the arch lifts and the big toe and heel get closer? Can you also feel what happens at the back of your ankle in the achilles tendon – how it shortens?
Roll back down and feel how the arch decreases – the tension at the arch is softer and the bottom of your foot is less tense.
You may also notice when you roll down that your ankle falls into whatever habitual movement pattern you have – does it tend to roll in or out when your weight is fully on the foot?
Spend some time over the next week playing with activating dorsiflexion of the big toe. Spend some time walking very slowly while barefoot and noticing how the foot changes at the arch through the various stages of gait. Notice if you tend to roll your ankle in or out while you bear the weight on your foot, notice if your toes don’t actually bend, notice if your arch feels stiff and high or collapsed without tone. Spend some time noticing.
References
Bolgla, L.A., & Malone, T.R. (2004). Plantar fasciitis and the windlass mechanism: A biomechanical link to clinical practice. Journal of Athletic Training, 39(1), 77 – 82.
Caravaggi, P., Pataky, T., Goulermas, J. Y., Savage, R., & Crompton, R. (2009). A dynamic model of the windlass mechanism of the foot: evidence for early stance phase preloading of the plantar aponeurosis. Journal of Experimental Biology, 212(15), 2491-2499.
Kaliniev, M.A., Krastev, D., Krastev, N., Vidinov, K., Ventchev, L., & Mileva, M. (2013). Abnormal attachments between a plantar aponeurosis and calcaneous.Clujul Medical, 86(3), 200 – 202.
