The Arch is constructed w/ the Tarsal joint and filled w/ soft tissues (ligaments, muscles, & fasica) as the major cushioning system for its weight-bearing function that is designed to handle 75% of the weight that falls to the bottom of the foot as you can see from the image. Under the heal and the ball of the foot areas are fatty tissues for minor cushioning system that are together designed to handle 25% of the weight that falls to the bottom of the foot.
In order to utilize the arch for 75% of the weight-bearing while keeping the Tarsal Joint in alignment, we need to use orthotics that align both anklebones at the same height, & the Anklebone Alignment test can prove if the orthotics are aligning the anklebones.