Adult-acquired flatfoot deformity is characterized by collapse of the medial longitudinal arch (Fig. 1) with failure of the supporting posterior medial soft tissue structures of the ankle and hindfoot [26]. Although pes planus can be attributed to arthritic, developmental, neuromuscular diseases, and traumatic conditions [1, 2, 4‐6, 11, 15, 18, 21, 26], posterior tibial tendon dysfunction remains the most-common etiology. Posterior tibial tendon dysfunction includes a wide spectrum of conditions affecting the tendon, with rupture, deformity, and secondary arthritis being among the more-severe sequelae. This condition has been estimated to affect approximately 5 million people in the United States [14].