13/08/2022
Very interesting read posted by Dr. Kirby. The subtalar joint is only one joint in our foot, shows how incredible our feet and surrounding structures really are.
It is like a perfect jigsaw puzzle! 🧩👣
Subtalar Joint Anatomy
Here is a beautiful illustration of the subtalar joint, its osseous components, articular facets and restraining ligaments in excellent paper by Fernandez et al from two years ago (Fernández MP, Hoxha D, Chan O, Mordecai S, Blunn GW, Tozzi G, Goldberg A. centre of Rotation of the Human Subtalar Joint Using Weight-Bearing clinical computed tomography. Scientific Reports. 2020 Jan 23;10(1):1-4).
Note that the talus, which has had it's lateral, posterior, anterior and interosseous/cervical ligaments transected in this illustration, has anterior, middle and posterior facets which exactly match to the corresponding facets of the calcaneus. These facets make up the subtalar joint.
In addition, please note the very strong interosseous talo-calcaneal and cervical ligaments which tightly bind the central bodies of the talus to the calcaneus together to help prevent distraction of the talus away from the calcaneus during weightbearing activities. The interosseous and cervical talo-calcaneal ligaments are the key to allowing the subtalar joint to have a relatively constrained set of joint axes which form a tight bundle of axes even with external forces which act varied directions on the plantar foot from ground reaction force (Van Langelaan EJ: A kinematical analysis of the tarsal joints: An x-ray photogrammetric study. Acta Orthop. Scand., 54:Suppl. 204, 135-229, 1983).
Finally, realize that the talus is the only bone of the foot to directly articulate with the bones of the leg, the tibia and fibula. Therefore, the rotations, translations, forces and moments of the tibia are directly transmitted to the foot by the talus rotating and translating at the subtalar and midtarsal joints during all of our daily weightbearing activities. What a marvelous piece of engineering and design the human foot is!
