“Lift your toes to ground down…elevate your arches…don’t allow your foot to roll to the inner edge…” All easily executed actions in standing poses, until it feels like someone is driving a nail through your foot. By and large, we trikonasana, utkatasana, and tadasana our way through our practice with relatively little thought about the feat (pun intended) of engineering that makes these poses possible: the arch. Moreover, we may be even less aware of the Fibularis Longus and Brevis and Tibialis Anterior and Posterior—the extrinsic muscles of the foot that when healthy keep our arches strong and us upright, but when compromised can leave us painfully hobbled.
Before we explore foot arch anatomy and how these muscles support us, here’s a little primer about the structures we stand on:
The bricks: The heel, or calcaneus, is obvious to us (especially when breaking in new shoes) as are the phalanges, or what we see as our toes. The bones in between look like an intricate 3D puzzle. Moving from heel to toes, the talus sits on top of the calcaneus, between the tibia and fibula (lower leg bones) and is notched in to the base of the tibia much the way a mortice and tenon joint fit together, or the way a nut fits into a wrench. In front of the talus is the cuboid, on the lateral side of the foot, and the navicular, on the medial side. These two bones comprise the apex of the foot’s arch. Continuing toward the toes, the navicular also interfaces with three cuneiforms, which along with the distal portion of the cuboid, connect to the metatarsals and finally the phalanges. The metatarsals and phalanges are numbered 1 through 5, big toe to pinkie toe. All together, these bones comprise the “arch” of your foot. But actually, we have three arches.
The structure: The medial arch runs along the inside of the foot, and is comprised of the calcaneus, talus, navicular, all three cuneiforms and the 1st through 3rd metatarsals. This is the part of the foot that leaves a blank spot on the pool deck when you get out of the water and walk back to your chaise, leaving fadingl footprints behind. Given the height and the number of small bones and joints in the medial arch, it is designed to be springy, propel us in our gait and absorb shock of vertical forces traveling up through our body. The lateral arch along the outside of the foot includes the calcaneus, cuboid, and 4th and 5th metatarsals. It is limited in height and movement and provides stability, and is the continuous portion (except for people with extremely high arches) in the wet foot print. The ‘half dome’ that spans the two is the transverse arch.
The mortar: In addition to the host of tendons, intrinsic foot flexors, extensors and of course, the plantar fascia (all subjects for later blogs), the Fibularis and Tibialis muscles of the leg play a critical role in keeping our arches healthy and the spring in our step.
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