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82 m a s s a g e & b o d y wo r k j u l y/a u g u s t 2 0 2 1 The Tibiotalar Joint Hotline to the Brain BY TIL LUCHAU technique | THE SOMATIC EDGE Balance isn't easy. Whether in our life or in our body, finding the sweet spot between life's extremes can be complicated. For example, simply standing upright is a tremendously complex balancing act. In order to stand, our brain must constantly monitor and respond to input from the environment via our eyes, from our movement in space via our inner ears, and from our body itself via sensory nerve endings (mechanoreceptors) in the soft tissues of the body. 1 Concentrated around joints, these specialized neurons talk to our central nervous system about mechanical force and position. In turn, the brain (specifically, the brain stem, cerebellum, and cerebral cortex) uses this information to orchestrate the reflexes, tension, and coordination we need to balance, stand, and move. THE TIBIOTALAR JOINT The lower in the body we look, the greater the forces of standing and balancing become. For example, the neck balances the head's weight, and the pelvis bears and balances the entire weight of everything above it. But the foot modulates more force than any other body part. This is especially true of the tibiotalar joint, where the tibia rests on the talus (the small, oddly shaped bone at the top of the foot). Here, the entire weight of the body is concentrated into a slippery, domed joint surface about the size of a quarter. 2, 3 Though the talus is unique in that no muscles directly attach to it, it is surrounded on all sides by layers of soft tissue (Image 1), including joint capsules, ligaments, tendons and their sheaths, retinacula, deep and superficial fascia, and skin. All these are richly embedded with mechanoreceptors that monitor the enormous forces at this crucial joint and rapidly communicate this information to the brain. It is thanks to this stream of sensory information that we're able to balance on the relatively small tibiotalar platform. Without the mechanoreceptors arrayed around the tibiotalar joint, the brain could not sense, prioritize, or respond to changes of ankle angle, position, or load, and walking would be impossible—often as not, we'd simply fall over. HOTLINE TO THE BRAIN As an analogy, a hotline was set up directly linking the Pentagon and the Kremlin in 1963 at the height of the Cold War, so that crucial, disaster-averting communication could be prioritized. The tibiotalar joint can also be thought of as a kind of hotline to the brain because of its key role in disaster-averting (that is, fall-averting) balance. As hands-on therapists, we can imagine using this joint's unique capacity At the tibiotalar joint, the concentrated weight of the entire body balances on the talus (blue). Surrounding this quarter-sized articulation, mechanoreceptor- rich structures send a stream of information about position, stresses, and movement to the brain, which coordinates the complex reflexes and muscular activity of balancing, standing, and moving. (Purple: toe flexor group. Brown: peroneal group. Dark green: Achilles and plantaris tendons. Orange: extensor group. Brown, tan, and green wrappings: skin, superficial and deep fascia, and retinacula.) Anatomy image courtesy Advanced- Trainings.com. 1