Adult flatfoot can be defined as loss in the height of medial longitudinal arch and it either persists or develops after skeletal maturity. Existing deformity can cause pain, instability and significant functional limitations or can be asymptomatic. This situation is usually called as `posterior tibial tendon dysfunction` or `adult acquired flat foot deformity` because it is mostly seen as a result of posterior tibial tendon degeneration.

Flexible flatfoot, posterior tibial tendon dysfunction, trauma, arthritis, iatrogenic deformity, neuropathic arthropathies (Charcot), neuromuscular diseases and tarsal coalition can be listed in the etiology.

Asymptomatic patients do not need treatment. Conservative treatment is the first choice in symptomatic patients; activity modifications, strechting exercises, manipulations, serial casting, weight loss, medical treatment for pain and inflamation, shoe change or modifications, use of orthoses can be listed as conservative treatment modalities. Patients who are still symptomatic after conservative treatment are candidates for surgical treatment and soft tissue procedures (synovectomy, tendon repair or tendon transfer) or bony procedures (lateral column lengthening or medialization osteotomies for calcaneus, medial cuneiform osteotomies, arthroereisis, double or triple arthrodesis in cases with joint degeneration) can be used according to the cause and severity of the deformities.