Posterior tibial tendon dysfunction (PTTD) is a problem with the tendon connecting one of the lower leg muscles to the foot bone. PTTD can cause pain, swelling, and a flattened foot and may require surgery if left untreated. Normal treatment for PTTD includes physical therapy exercise. In treating similar conditions in the lower leg, exercises that are active, like strengthening, seem to have better results than exercises that are passive, like stretching. This study will determine whether adding strengthening exercises to a normal PTTD treatment that includes wearing a brace and stretching is more beneficial than just wearing a brace and stretching.