Foot Basics Summary

The bones of the foot are constructed to form three arches, which together provide strength and stability to the foundation of the body:

• Medial longditudinal arch (biggest arch, along the inner side of the foot),
• Lateral longditudinal arch (smaller arch along, the outer side of the foot)
• Transverse arch, (across the front part of the foot, between the big toe and the little toe).

The structural integrity of each of these arches is provided by 3 "keystones" - the Talus, Cuboid and Middle Cuneiform.

The soft tissues (muscles, ligaments and tendons) provide the necessary flexibility to this bony three-arched structure, allowing all the arches to heighten (tighten and contract) and lower (loosen and expand) to facilitate proper foot function throughout the Gait Cycle.

With every step we take, foot function is controlled by the constant alternation between the states of mobile adapter and rigid lever. This is achieved by utilising the motions of pronation and supination respectively at the Sub-Talar Joint.

The position of the 3 "keystones" (Talus, Cuboid and Middle Cuneiform) is critical to proper foot function. Any mis-alignment of these bones, or other bones which in turn affect the alignment of these three bones during the gait cycle will cause disruption to the degrees and timing of pronation and supination at the sub-talar joint. As these motions control the sequence and timing of the entire gait cycle, any misalignment of the keystones disrupts the function of the entire foot.

Because the foot lies at the base of the kinetic chain and is the only part of the body that relies on interaction with outside forces (the ground surface), the structure and function of the foot is critical to providing strength and stability throughout the rest of the kinetic chain.

The degree and timing of pronation and supination that takes place within the foot directly affects the degree and timing of internal and external rotation of the lower limbs. As each bone is connected to another throughout the human body (closed kinetic chain), any problem in the biomechanical function in the foot means a problem in the biomechanical function of the rest of the body.