The adult flat foot What can cause a flat foot and how ?
The straight forward way to look at this is which of the above factors can malfunction and why?.
The following list is not in order of merit or frequency. Probably the most common cause of a flat foot in the adult is inherent ligamentous laxity (known as a physiological flat foot, and a variation of normal), followed by disease of the Tibialis posterior tendon. The medical conditions mentioned in the following list are to be found in the glossary.
1) Bones /joints :Fractures :By disrupting the normal bony architecture of the arch or/and the way the joints sit Arthritis: Also by destroying the normal alignment of the joints (and sometimes the tendon and ligament as well). Any form of arthritis may result in this condition. A particular type to watch out for is known as Charcot Arthropathy. This can result in a rapid and very severe, progressive loss of the arch.
Developmental :A condition called Tarsal Coalition exists which results in the bones of the midfoot foot fusing together abnormally and results in a fixed flatfoot deformity . 2) Muscle / tendon: Tibialis Posterior Dysfunction : This tendon lies on the inner border of the foot and has a vital in maintenance of the arch. It lengthens when diseased and inflammed, contributing to a loss of the arch and the appearance of a flat foot. Polio
Accessory navicular: an additional and longstanding piece of bone occurring at the point of tibialis posterior insertion into the foot. This may become symptomatic and lead to a flat foot deformity.
3) Ligament : Ligamentous laxity(Physiological flat foot) Spring Ligament rupture : Due to trauma or Inflammatory arthropathy. | 
