Category: Applied Functional Science
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The subtalar joint is critical for success in the Chain Reaction of movement.  The position of the subtalar joint affects directly the mobility of the foot.  Motion of the subtalar joint causes movement up the kinematic Chain Reaction to the knee, hip, and spine.  It is important to learn about the complexity of the subtalar joint.  But, it is essential to appreciate the practical simplicity of the joint during functional movements.

Part of the complexity is pseudo-complexity because it is really confusion created by the terminology used to describe the motion.  The most common terms used to describe subtalar joint motion are pronation and supination.  The motion is labeled uni-axial, but tri-planar.  Uniaxial means only one motion occurring perpendicular to that single axis.  The motion is tri-planar because the orientation of the axis results in motion occurring in all three planes (primarily frontal and transverse).

Pronation and supination refer to the relative joint motion.  Which real bone motions will create those relative joint motions?  Let’s start from the bottom-up.  If the bottom of the calcaneus moves away from the midline of the body in the frontal plane that real bone motion is called calcaneal eversion.  In almost every case, if the calcaneus everts (either weight bearing or non-weight bearing) that eversion causes pronation at the joint.  Since the subtalar joint is tri-planar, whenever it everts in the frontal plane there will also be motion in the transverse plane.  The terms for this motion are either abduction or external rotation.  So when pronation occurs at the joint, the calcaneus everts in the frontal plane, externally rotates in the transverse plane, with a little sagittal plane dorsiflexion.  Since the joint is uni-axial, these motions can not occur separately.

When the foot is weight bearing, the real bone motion of the calcaneus is accompanied by real bone motion of the talus above.  Because of the pitch of the axis, the subtalar joint acts as a torque converter.  Frontal plane motion of the calcaneus is converted into transverse plane motion of the leg above.  The eversion of the calcaneus creates real bone internal rotation/adduction of the talus as part of the (relative) subtalar joint pronation.  Since the talus has very little transverse plane motion in the ankle joint, the internal rotation of the talus causes the lower leg to internally rotate.  In many situations, the Chain reaction continues with the femur going through real motion resulting in relative joint motion at the hip.  This amazing Chain reaction sequence will occur top-down as well as bottom-up.  In upright function whenever the femur internally rotates, the lower leg likely will internally rotate taking the talus with it.  The motion of the talus creates relative joint pronation and cause the calcaneus to evert.

Both the bottom-up and the top-down biomechanics described above will occur in reverse with relative subtalar joint supination.  Being able to evaluate the subtalar joint’s ability to move and the extent of that motion while weight bearing (and integrated with the rest of the body) is an essential “tool” required by all movement practitioners.  3DMAPS utilizes both bottom-up drivers (lunges) and top-down drivers (arm swings) to create subtalar joint pronation and supination as part of global functional movements.  The ability to analyze the influence of the subtalar joint on the rest of the body, as well as the body’s influence on the subtalar joint is the power of 3DMAPS.

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3 thoughts on “Chain Reaction Biomechanics – Relative from Real: Subtalar Joint”

  1. I’m pretty much a lay person here, massage therapist, who tries to pay attention to the chain as I work. And here I read an explanation of the problem, or description of how correct functioning should occur, but now I m anxious to read solutions for getting that subtalar joint open and mobile. I can tell you from personal experience your description makes total sense. I broke my right ankle as a child and have a “stuck” subtalar joint. I do lots of stretches, use a foot massager machine that moves all the tissue in the foot and lower leg via vibration, and the Core Conversion helps greatly. I also have to keep up some spin, rowing, the stepper elliptical, and squats to stabilize or strengthen around the knee and the hip. If I don’t, the chain collapses and I have lots of pain in the rt knee, rt hip, low back and/or left Achillies. Every day is a new adventure when I don’t keep thing up. Maintenance is constant. So, any tricks to open that joint more permanently for me, and not have to be so efforting daily on this “problem area”? Thanks for any help!Sorry this is long.

    1. Esther,

      Thanks for your comments on the subtalar joint blog. As a massage therapist, you have a great opportunity to enhance the lives of others that seek your services.

      Your personal experience is not uncommon. Your frustration is real, and your search for more lasting improvement is valid. Someone who practices with a Applied Functional science mindset would use a two-pronged approach. One is to work on your hip while minimizing the negative effects of your existing subtalar restrictions. At the Gray Institute, we would call this a top-down approach.

      Someone using the Principles of Applied Functional Science would also work on your subtalar joint, possibly starting with the plane of motion where you have the most success. You might also have ankle and mid-tarsal joint restrictions that might be less resistant to improvement. These joints can be leveraged to improve the subtalar joint.

      I do not know where you live, but there might be a GIFT Fellow who has completed our 40-week mentorship program in your geographical location. On the main page of the Gray Institute website at the bottom there is a way to locate a Fellow. Also, you can take advantage of the free content on the Gray Institute website if you have not done so already. Please look into a device called an Air Baps that you can order for yourself to facilitate a bottom-up approach to your foot to hip Chain Reaction.

      Finally, you might want to consider enrolling in our GIFT program. We have had many massage therapists enhance their skills and expand their practice by completing GIFT. The resolution of your personal impairments could be the gift you give yourself.

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