Flatfeet are a common condition of the foot structure. In infants and toddlers, prior to walking, the longitudinal arch is not fully developed and flatfeet can be normal. Most feet are flexible and an arch appears when children begin standing on their toes. The arch continues to develop throughout childhood, and by adulthood most people have developed normal arches.
Flatfeet are generally associated with pronation, a leaning inward of the ankle bones toward the center line. Flatfeet develop due to posterior tibial tendon dysfunction or PTTD. The posterior tibial tendon starts in the calf, stretches down behind the inside of the ankle, and attaches to bones in the middle of the foot. This tendon helps hold the arch up and provides support when stepping off on your toes when walking. If it becomes inflamed, over-stretched or torn, it can cause pain from the inner ankle. Over time, it can lead to losses in the inner arch on the bottom of your foot and result in adult-acquired flatfoot.
There is generally pain and swelling on the inside of the ankle. Also, there may be weakness and an inability to stand on the toes. Sometimes people complain that their foot is still growing because the shoe size has increased; this is instead the foot elongating as the arch collapses. People who are diabetic, overweight, or hypertensive are particularly at risk.
Left untreated, posterior tibial tendon dysfunction may lead to flatfoot and arthritis in the hindfoot. Pain can increase and spread to the outer side of the ankle. Treatment includes rest, icing, nonsteroidal anti-inflammatory medications, physical therapy, taping/bracing, custom molded orthotics (arch supports), and immobilization of the foot for six to eight weeks with a rigid below-knee cast or boot to prevent overuse. Surgical repair of a weakened tendon, a screw implant to limit pronation, or even bone procedures may be necessary.