Several external and bodily influences prompt adult flatfoot, a deformity resulting in a fallen arch. Patients may treat the condition with orthotics or braces, but if no relief arises surgery can be an effective alternative.

Damage to the posterior tibial tendon is the most common cause of adult flatfoot. The tendon supports the arch and foot as you walk. Starting at the calf muscle, it travels down the lower leg and attaches to the bones inside the foot. If the tendon is inflamed or torn, the arch will collapse over time. Individuals over the age of 40, primarily women, are most likely to develop issues with the posterior tibial tendon. Those who participate in high-impact sports may slowly tear their tendon from repetitive use.

Inflammatory arthritis also induces flatfoot in adults. Arthritis targets the cartilage in the joints and the ligaments supporting the foot. The effect produces extreme pain and alters the shape of the foot. Arthritis affecting the back or middle of the foot strains the ligaments, ultimately collapsing the arch.

Injuries of the ligaments in the foot often push the joints out of alignment. These ligaments support the bones in the foot and stop them from moving out of place. If there is a tear, the foot has no support, causing the arch to fall. This type of damage typically occurs in the middle of the foot (Lisfranc injury).

People with diabetes with nerve problems can also suffer from arch collapse. Some individuals living with diabetes suffer from nerve problems, which affect their ability to feel sensations in their lower extremities. Arch collapse in diabetics can be more severe because of their insensitivity. In some cases, the bones can fracture and disintegrate without the patient feeling any pain. The foot may deform severely, making surgical correction difficult.