Posterior tibial tendon dysfunction (tendinitis, tendinosis, or rupture) and adult acquired flatfoot deformity can manifest with a wide array of bony and soft tissue abnormalities visible on plain radiographs, ultrasound, and magnetic resonance imaging. Imaging abnormalities include various combinations of malalignment, anatomic variants, and enthesopathic and tendinopathic changes. A thorough understanding of differences between anatomic and pathologic presentations of structures in various imaging modalities is an essential tool for clinical and surgical planning.