The foot is comprised of 26 bones (creating 33 joints) all of which work synergistically to create a strong, stable and flexible platform, allowing effortless interaction between the body and the world around us.
The sinus tarsi is an anatomical tunnel, basically a space or hole, created by two bones; the talus and calcaneus bones (which together also create the subtalar joint). It is located on the outside of the foot, just in front of your large bony bump (called the lateral malleolus) and the tunnel continues deep into the foot.
The sinus tarsi provides stability to the joints of the rear foot during inversion and eversion movements. It is filled with adipose (fat) and connective tissue and is rich in nerve endings and proprioceptive cells (cells used to provide sense of awareness of body position, increasing balance and stability) (Helgeston et al., 2009)