Subtalar arthroereisis as an adjunct procedure may hold promise for patients who have mild and more severe variants of posterior tibial tendon dysfunction (PTTD). The biomechanics of the implant function have not been fully elucidated, and questions remain about the best clinical indications for the device. This article reviews the limited existing literature and describes the author's personal experience testing subtalar arthroereisis in the laboratory and using the implant clinically for correction of adult flexible flatfoot.