Flat feet is when the arch of the foot comes in contact with the ground. This can be a normal condition. The causes for flat feet can be congenital, in that you're born with it, or acquired, which develops with age.
Acquired flat feet typically occurs secondary to wear and tear on the tendon on the inside of your foot called the posterior tibial tendon. Through repetitive trauma or acute trauma, this tendon can weaken and the arch can lower.
Flat feet may not hurt. Some people just have flat feet, and it may not be a problem all their lives. However, there are quite a few conditions that are associated with flat feet. The development of bunions and hammertoes is common with people with flat feet. The development of heel and arch pain is also common with people with flat feet. Flattened feet can lead to pain in your ankle, your knee, your hip, and ultimately your lower back.