By Maggy Ashby, RMT

Today, we walk through an ancient wonder – a biological system predating Egypt’s pyramids:  The arches and bridges of the human foot. 

The design and mechanics of the foot deserve respect:  The system leverages twice your body weight across it at each step.  

Two common conditions of the foot collide:

In the last episode we started to formulate solutions to the questioner who mused, 

“Do I need to buy wider shoes now that my toe is turning in?”

Our solution for her will evolve. 

We first considered the muscles that hold the hallux square (see last episode).  

thinking woman
thinking woman

Her second question was,

 “Can I do anything about fallen arches?”

A more fulsome answer to big toe problems emerges in the context of the foot’s arches and bridges.

So, in this fourth episode we wade into her second question, as a more complete answer to the first. 

Here in episode four, the two problems she poses intersect. 

Back on the Foot Pain Trail, we find ourselves in cavernous landscape – shadowed by natural arches, and bridges made of stone – I mean bone.

The foot’s design reminds me of our Marmot tent:

Figure 1:
arches

We are looking at the foot (above), of course:

  • A flexible bridge (like a rope bridge) extends from the hallux across the other toes. This bridge is called the anterior transverse arch.
  • The natural arch, running perpendicular to the flexible bridge, and also originating at the hallux is the (medial longitudinal arch or MLA). Our path follows this bridge, which spans from hallux to heel. 
  • At the apex of the ML Arch, we can watch the operation of another arc of interest in this natural system: The tarsal bones of the midfoot lock and unlock as the body’s weight shifts across them, between heel and toes. 

Tarsal bones form the posterior transverse arch.

 

This is how it looks when we superimpose the foot in place of a tent:

Figure 2:
foot arch

Big toe extension starts a chain of events with effect to the heel end of the foot:

Without the aid of muscles, our body’s weight, in combination with ligaments fashion a …

… Windlass Mechanism.

You have seen one, somewhere. 

 

I need look no further than our local UNESCO World Heritage Site to see one:

 

Locks of the Rideau Canal open and close via a windlass.

The windlass system at right provides access to this well’s cistern for garden water.

windlass
windlass
well and windlass

Modern sailors weigh anchor or fishing trawls through a windlass.

A windlass consists of a

  • lever,
  • drum to wind around,
  • and a chain or rope.

How a windlass works in the foot(1):

From Figures 1 and 2:   The orange plane (Figure 2) represents the tent floor (Figure 1).

The tent’s floor in the foot is the Plantar Aponeurosis, (fascia).

This is a huge ligament at the end of our Windlass.

The toes (particularly the hallux) are the windlass levers.

The big toe extends, turning the lever.  This winds the “chain”, or the plantar fascia.

The fascia ensconce the sesamoid bones

The plantar pads and boney plates wind around the windlass “drum”, or the hallux joint.

The tent floor (held fast at the heel) goes taut — which increases the height of the (ML) arch. 

When you walk, your body weight shifts forward, which forces your toes to extend.

No muscles required. 

Sesamoids / Sesame seeds:

It is no coincidence these words look the same. 

It is also no coincidence that the seed and the bone look alike.  The bone was named with the Greek word for sesame seed in mind.  

We encountered the sesamoid “boney armour” in the last episode.Fauna on the Foot Pain Trail; anchoring the big toe.

In Figure 3 they resemble their sesame seed namesakes, under the big toe.

The sesamoids shift to face the floor with the winding of the windlass.  In doing so, they shield the muscle that passes between them, and the head of the metatarsal, from being crushed against the floor by your weight.

The sesamoid bone’s presence attests to the big toe joint’s function as weight bearer — protector and nurturer if you take the Nordic eponym (“Allex — Hallux”).

Adding to the anatomical compass in the Guidebook:

I did mention that this page of the guidebook would get very well thumbed. 

In episode two you learned,

  • flexion,
  • extension,
  • abduction and
  • adduction

To have a meaningful discussion about your arches, you need two more terms in the glossary. 

We touched on them last month.

  • Supination rolls your instep away from the floor (also known as inversion).

 

  • Pronation is the opposite (a.k.a. eversion):
foot

Pronation flattens your arch, rolling your ankle and elements in your foot towards the floor.

 

“Inversion and eversion” seem in reverse — I thought of them in relation to the arch. 

 

But if you relate the terms to your heel bone, they make more sense. 

 

An instructor gave me a helpful memory aid for “supination and pronation”:

“sup is up”.

This topic is a big one, so I’ve split it over two months. 

Next month we discover the main characters that live at the footing of the bridges.  Blogs 2 – 5 (inclusive) give you needed background information about your big toe, and arch support.  

Episodes 6 and 7 touch on two other related areas of the foot, that are essential to its overall mechanism, and structure. 

In episode 8, we put it altogether and try exercises to recover function.

 Tune in next month for episode five, and the conclusion to “Foot bridges: Ancient world wonders that factor in foot pain.”

… to be continued ….

References

(1) John Hicks laid out the windlass mechanism in the foot really well in 1954.

 

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