My coworker and I recently wrote an article on the biomechanics of the Talus that got published in the Anatomy Trains e-Magazine! I think ya’ll would really enjoy it! Audio version coming soon 🙂
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Ida Rolf wrote that “problems in the upper body vanish as the feet ‘understand’ them.” She also labeled feet “tattletales.”[1] Are you a movement teacher, a manual therapy practitioner or both? You probably work with feet all day long. You fully appreciate that feet need neuromyofascial organization, and pliability. You know that good foot-awareness is essential in order for the people in your care to “under-stand themselves.” Have you seen feet that “tattle” on the goings-on upstream? Admittedly, to fully understand the marvelous mechanics of feet takes some effort. Rigid models, architecture inspired descriptions, thick books and heady papers have caused more than a little confusion about the biomechanics of feet. Sadly, as a result, some of us have misunderstood the feet we are trying to help- feet that desperately need to stand under their owners.
Many practitioners crave clearer explanations of foot biomechanics. If you are in that camp, don’t fret, you are not alone. In this article we will make some aspects of foot biomechanics crystal clear. A few simple metaphors might just give you an understanding you’ll regift to your clients and students.
Understanding is the ability to relate the parts to the whole. To understand feet, we need to grasp the workings of the parts. We will elucidate the shape and behavior of several foot structures and zero in on the talus. Understanding how these parts work will help you visualize how the entire foot moves. But, this is only a summary of the story. We’ll save the rest for future articles. But we gotta start somewhere! To get us “off on the right foot,” let’s start with your two feet, in four.
Your Two Feet in Four
Ida Rolf offered another helpful explanation of the “tattletales” she knew so well: “an inner longitudinal arch rides on top of an outer longitudinal arch.” [1] Some say this in a more confusing way by referring to this construction as “heel foot” and “toe foot.” To provide some clarity, Tom Myers works this out for us in Anatomy Trains with the “canoe” and“outrigger” illustration. [2] To keep it even more simple, we can think of the two arches as the “inside foot” and the“outside foot”.
Figure 1:
Knowing which bones make up our inside foot can help us assess standing bodies. Knowing how the inside foot rides on top of and slides away (unlocks) from the outside foot will help us assess moving bodies.
We can see the beauty in the relationship between the inside foot and the outside foot when we understand three things:
- The “two” feet primarily connect to each other to become one foot between the talus and calcaneus.
- In the walking gait cycle the outside foot contacts the ground before the inside foot by means of “heel strike.”
- In gait, when the foot accepts the weight of the body the outside foot tilts medially (inward) and nods downward, presenting the inside foot to the ground. The inside foot slides away from (unlocks) from the outside foot.
You stand on two feet. You walk on four, at least for a moment. When the inside foot unlocks from the outside foot your inside foot is accepting the weight of your body, conforming to the ground. In this way it expands into all its fascial riggings and wrappings. This generates useful spring loaded tension and lots of information for later in the cycle. See? Everyone has two left feet… until they don’t. But let’s suss out just how the inside foot is encouraged to slide away(unlock) from the outside foot.
Tell-Us About the Talus
Look at the shape of the talus in figure 2. Notice how the talus and heel connect to each other in three places. The hollow space between those joints is called the sinus tarsi. It contains blood vessels, fat, nerves and of course, organized water. Can you see how the talus rests on a tray-like projection on the calcaneus? If the “tray” were to tip what do you think would happen to the talus? We’ll get to that. Just know that this relationship between the talus and calcaneus is referred to as the subtalar joint.
Figure 2:
Turn your attention to the top of the talus. It looks like a saddle; doesn’t it? The bottom surfaces of the tibia and fibula are also saddle shaped. These two saddle shapes connect to form the ankle joint. Can you also see how the fibula and tibia hold on to the talus? Gary Ward, author of What The Foot aptly describes the talus/fibula/tibia relationship as a head wearing headphones. [3] The talus is the head and the malleoli of the fibula and tibia (ankle bones) are the headphones.(Figure 3) As Mr. Ward puts it, the talus is “the driver of the bus” and “where the talus goes, the whole body will follow.” When the talus moves, the headphones follow. The word “crural” is used to refer to things related to the lowest part of the lower limb, where the tibia and fibula live. The tibia, fibula and talus form the talocrural joint.
Figure 3:
Through it’s neck, the talus reaches out to the navicular. The “ball” of the end of the talus fits in the “socket” of the navicular. The talus is poised to push the boat-shaped navicular bone.
So how does the talus move in walking? Thought you’d never ask! If you can understand how the talus moves, you can understand how the inside foot unlocks from the outside foot, via the subtalar joint, sliding toward the ground when your foot accepts the weight of your body.
In walking gait, when your leg swings forward to prepare you to step, your calcaneus flies through the air in a laterally tilted position. When it lands, it’s outside back corner lands first. Viewed from the back, the calcaneus is lopsided (careful,some anatomy apps fail to render this tilted shape of the bottom of the calcaneus). Due to it’s shape and the speed with which it contacts the ground, after landing, a healthy calcaneus will abruptly tilt inward. It also tilts forward like a ball rolling down a hill. What happens next is explained well by James Earls in Born to Walk. After heel strike, and as your foot begins to accept the weight of your forward traveling body, your tibia and fibula “pivot in the talar joint, similar to a vaulter’s pole.” [4] These are the events that occur below and above the talus in the weight acceptance part of walking gait. But what about the talus itself?
It’s during the weight acceptance part of our gait that we can really see the talus do it’s “thing.” Since the tibia and fibula have pivoted, bringing the rest of the body along, the load on the talus from above is greatly increased. The calcaneus also tilts inward and rolls forward. As a result, it’s waiter’s tray is tilted toward the ground. Picture a waiter bowing to lower a tray. (Figure 4) This lowers support for the talar head. Increased weight from above? Support removed from below? What is a talus to do? These changes cause the talus to tilt inward and to rotate downward, away from its nestles in the calcaneus. This motion unlocks or expands the three articulations between the talus and the calcaneus. Thus, the inside foot slides away from the outside foot.
Figure 4:
To picture the movement of the talus during the weight acceptance part of gait, make a fist with the back of your hand toward the ceiling. Now flex your wrist toward your torso (radial deviation). Then flex your wrist toward the floor. That’s roughly how the talus moves during gait, unlocking the inside foot from the outside foot.
To use clearer language we prefer to use the description “joint expansion” instead of “unlock.” Besides a separation from the outside foot, the talus drives more expansion to help your foot adapt. Remember, the talus is buddies with the navicular bone too. During its weight-acceptance-dance, it nudges the navicular bone. The shape of these two bones and the angle of force from the movement of the talus expands the space between them. This chain reaction expansion continues down the inside foot.
As you visualize the movement of the talus and how the inside foot is presented to the ground by the outside foot, please do not miss this key takeaway: healthy feet need access to LOTSO’ medial tilt (pronation). Arches in feet need to“collapse” and expand, “fall” and rise. That’s adaptability. If we cling tightly to unyielding architectural metaphors and encourage stability at the expense of adaptability, the feet we influence and the bodies above them will also be rigid. Your manual work and movement teaching can be good medicine for feet that need to access more adaptability.
We have explained that during the weight acceptance part of gait, after heel strike, the calcaneus abruptly tilts inward and rolls forward. With the tibia and fibula pivoting to shift the body’s weight over the planted foot, the talus is loaded from above. In response to the movements of the calcaneus below and the increased weight from above, the talus tilts and rotates inward. These are descriptions of how the bones move. Let’s take a quick look at the behavior of the joints, the spaces between the talus and its friends.
Why the talus is like T12 upside down
We mentioned the three bottom side articulations the talus has with the calcaneus. Topside, it also articulates in three places. The talar dome articulates with the tibia, and then each side of the talus connects to the medial malleolus (part of the tibia) & lateral malleolus (part of the fibula). This saddle-in-saddle-shaped (some say mortis and tenon) relationship between the tibia, fibula and talus allow the foot to dorsiflex and plantar flex. This is a motion that happens predominantly in the sagittal plane (think “plane in which a bicycle wheel rolls”). On bottom, the three joints between the talus and calcaneus allow the talus and calcaneus to rotate relative to each other in the transverse plane (think “plane in which a plate could slide or rotate on a tabletop”).
Said another way: above the talus, the talocrural joint engages in sagittal plane movement. Below the talus, the subtalar joint rotates in the transverse plane. In this way the talus is like T12 upside down. The arrangement of the facets between T12 and L1 (below T12) only allow those joints to move predominantly in the sagittal plane. The arrangements of the facets between T12 and T11 (above T12) only allow those joints to move in the transverse plane. T12 is a diplomatic bone, allowing for one type of motion above and another below. Like a U-Joint or a CV-joint, it converts some of the motion in one plane to motion in another plane. In a similar way, some of the aspects of talar movement involve taking energy from movement in one plane and using that energy in another plane.
Rotation, Rotation, Rotation
Ironically, in order for us to propel ourselves forward in the sagittal plane, our bodies use a lot of rotational motion in the transverse plane. We can see evidence of this in the wind-up action of the ribcage. In order to harvest rotational force from the ground, somewhere in our bodies something has to convert the upward traveling ground reaction force into rotational force and then drive that energy upward in spirals. That kind of energy conversion, of course, is initiated by the action of the subtalar joint. When the talus responsively rotates, the headphones (tibia and fibula) follow that rotation. The rotation of the tibia causes the femur to rotate in the same direction. The femur’s rotation, combined with the energy from the leg swing, will cause the pelvis to rotate in the same direction. [4] The sacrum and lumbars follow suit, all rotating in… you guessed it, the same direction. The arms and rib cage (rib basket) rotate in the opposite direction. All this rotation is resolved in the spine so that our head can point our eyes forward. We don’t want our heads swinging in the “no” motion while we walk. But thanks to the subtalar joint we move forward using rotational energy. Can you see the benefits we derive from encouraging healthy medial tilt of the inside foot?
Fascial Hammock
Take a few minutes to study figure 5. Visualize the deformations that will occur in the following ligaments:
- The deltoid ligament (between the tibia and navicular, tibia and talus, tibia and calcaneus)
- The plantar calcaneonavicular ligament (the wide springy ligament that spans between the sustentaculuum tali and the navicular and which forms the floor of the talonavicular joint) [5]
Picture the twists and tensions these tissues feel as the tibia tilts anteriorly and also transfers the weight of a walking body downward. Picture the stretch that would be sensed as the talar head pushes down and into this hammock-like fascia. Can you see how the longitudinal fibers would be loaded not only from the pressure of an inwardly rotating talus but also by the inward tilt of the calcaneus?
Figure 5:
The fibrous tissues associated with the inside foot receive oodles of “stretchy,” “tensiony,” “twisty,” “loady” information as we walk. Can you see how these tissues could be begging for your therapeutic input? By studying fiber directions and imagining how they behave as the bones move we can formulate manual or movement approaches that will lengthen, widen, unstick, wake up or settle down these sensing tissues.
Should We Work to Restore Arches?
When guiding someone into a better relationship with gravity, we sometimes need to help feet find more space under themselves. As structural integrators, we spend time looking with our clients at their feet in a standing position. It has been suggested, by Tom Myers and others, that standing assessments allow us a glimpse at how a person is choosing to“be.” This sort of body-reading may pull back the curtain on body schemata or maps that live on the rind of the brain. A standing assessment opens up questions like: “What is this person’s sense of self?” or “How are parts relating to their whole?”. However, moving assessments can give us brighter views of deeper neural patterns, motor maps and networks that represent relationships with the outside-self-world. (For movement assessment ideas see figures 6 & 7)
When assessing how the inside foot relates to the outside foot, it is more than worthwhile to ask our students and clients to move. If we assess feet in standing positions only, we may miss valuable information. One common mistake in foot work is to overemphasize good arches. In a standing assessment, the inside foot may look like the lofty arches podiatrists prize. But we need to know if feet are adaptable. Will that nicely elevated inside foot slide away from the outside foot when loaded? Will the talus rotate and tilt downward? Does it bulge into and spread ligaments of the ankle? Does it expand other tarsal joints, preparing the foot to mold onto stepping surfaces and to gather energy from the ground?
Monika Volkmar, creator of the Liberated Body Workshops based on the work of Gary Ward (Anatomy in Motion), states the principle point this way: “Pronation and supination are meant to be verbs, not nouns- pronating and supinating. The body should have dynamic access to both options…of the foot motion spectrum, not stuck in one or the other.”
It’s important to remember, there is such a thing as too much support (exempli gratia, learned helplessness). As structural integrators and movement teachers, we need to help the inside foot find its full range in both pronation and supination. In a structural integration series, opportunities to restore full movement to the inside foot can be found during inseam or lower deep front line work. In movement teaching, cues to help people relax the inside foot toward the ground counterintuitively create self supported arches. Ask yourself: am I inhibiting natural movement of the talus by too much arch-lift cueing?
When we sense that we are fully understood we open up, we relax. Speaking psychobiologically, bodies that are open and relaxed are usually standing under themselves. As practitioners, letting go of rigid approaches and encouraging healthy inside foot expansion will help those in our care access this understanding. As you do your good work to restore foot pliability, enjoy the results! You’ll see the bodies you work with open up and relax, standing under themselves with feet that are free to move, easily harvesting energy from the ground.
Figure 6&7:
[1] “Feet: The First Challenge.” Rolfing, by Ida P. Rolf, Healing Arts Press, 1989, pp. 45–61.
[2] “The Spiral Line.” Anatomy Trains: Myofascial Meridans for Manual and Movement Therapists, by Thomas W. Myers, Churchill Livingstone/Elsevier, 2014, pp. 148–149.
[3] “The Forgotten Body Part.” What the Foot?, by Gary Ward, Soap Box Books, 2014, pp. 110–134.
[4] “The Mechanical Chain.” Born to Walk Myofascial Efficiency and the Body Movement, by James Earls, North Atlantic Books, 2014, pp. 62, 64–66.
[5] “Ankle and Foot.” Kinesiology of the Musculoskeletal System: Foundations for Physical Rehabilitation, by David A. Neumann and Elisabeth E. Rowan, Mosby, 2002, pp. 491–492.