The causes of flat feet in adults are different and many. As one ages, and also due to diabetes and obesity, arches in the feet tend to flatten and can cause pain and dysfunction of tibialis posterior tendon, an important tendon that maintains normal arch of the foot.
- Arthritis: Arthritis may result in flat foot. Arthritis also causes ligament and tendon dysfunction causing flat foot. Charcot's joint occurs in diabetics particularly and causes a rapid and very severe, loss of the arch.
- Tibialis Posterior dysfunction: Primarily the important hind foot tendon called Tibialis posterior is responsible for maintaining arches. When the tendon gets damaged, TP tendon dysfunction (or TPPD) occurs, causing aching pain on standing and sometimes at rest, on the inside of the heel or ankle. This is an important cause of adult flat foot.
- Polio: lax ligaments also cause flat feet.
- Severe acute ligamentous rupture can cause rapid flat feet - Spring Ligament rupture.