Tendoscopy is a reliable and safe technique to manage some foot and ankle disorders. The technique allows for a view of the entire length of tendons and may be used as an isolated procedure or adjacent to other techniques, such as calcaneal osteotomy. Posterior tibial tendoscopy is a useful tool both for the diagnosis and treatment of different disorders that affect the tendon in isolation (i.e., post-traumatic) or in the scenario of a flatfoot deformity. We will review the technique of posterior tibial tendoscopy and present tips and tricks to optimize the tendoscopic experience. We will also analyze our first 20 consecutive cases of posterior tibial tendoscopy in the setting of a flexible flatfoot deformity and study our data and results. In 10 cases, there were no significant pathological findings on magnetic resonance imaging (MRI) or on tendoscopy. In six cases, synovitis and adhesions were informed on MRI and found on tendoscopy. Preoperative MRI findings were coincident with tendoscopic findings in 16 of the 20 cases (80%). MRI failed to identify two cases of synovitis, a case of synovial plica and suggested a partial tear where tendoscopy demonstrated no structural damage. Although MRI is an effective imaging tool for identifying tendon disorders, tendoscopy seems to be a more sensitive diagnostic tool. Posterior tibial tendon (PTT) tendoscopy has become our procedure of choice in stage IIA AAFD and has allowed us to treat PTT disorders when skipping the medial soft tissue repair with no impact on outcomes while addressing pathology that might cause symptoms if left untreated.