An off-the-shelf brace, the AirLift PTTD Brace is designed for the treatment of posterior tibial tendon dysfunction (PTTD), or for early signs and symptoms of the adult acquired flat foot. Depending on the severity of the condition, it can be prescribed for use as part of a conservative treatment to stabilize the condition and help prevent its degeneration, or post-surgically and during rehabilitation. Foot support and ankle stabilization are provided by the AirLift integrated aircell and semi-rigid shells. The aircell, located under the foot arch, is adjustable using the Hand Bulb (included with the brace). When inflated, the aircell can accommodate variances in arch shapes and heights and comfortably lifts the foot arch to achieve a more natural foot position. For ease-of-use, aircell inflation can be adjusted while wearing foot wear. The semi-rigid shells are anatomically designed to the shape of the ankle for secure support and stabilization. These shells help realign the ankle and support the patient. The AirLift is designed for easy application and adjustment. The brace uses an innovative rear entry design which allows the patient to slip their foot into the back of the brace. Two straps secure the brace and can be used to adjust fit. These patient-friendly design elements make the AirLift easier to apply than custom braces, eliminate time consuming lacing, and help improve patient compliance. Indication: Posterior tibial tendon dysfunction in stage I and early stage II; Adult acquired flat foot; Post-operative use; Rehabilitation