Adult acquired flatfoot is a deformity that develops when the arch along the inside of your foot flattens out after your skeleton has stopped growing, compromising your foot’s support. Your arch can “fall” for many reasons, but the primary reason an adults develops a flatfoot deformity is the weakening and rupture of the primary tendon controlling the arch, the Posterior Tibial Tendon. This runs along the inside of the ankle to its attachment on the foot. This condition is most common in middle-aged to elderly women, especially if they are sedentary.
Adult acquired flatfoot isn’t always painful, but a flattened arch puts additional stress on the heel and other joints, like the ankles and knees.