We describe a 2-portal endoscopic approach of the hindfoot with the patient in the prone position. By means of this approach, it is possible to visualize and treat a variety of posterior ankle problems. Not only can pathology of the posterior ankle joint and subtalar joint be visualized and treated, but also periarticular pathology, such as calcifications or scar tissue, can be diagnosed and treated. We describe a professional ballet dancer with chronic flexor hallucis longus tendinitis and a posterior ankle impingement syndrome caused by an os trigonum of both ankles. The patient was successfully treated by removing the os trigonum and releasing the flexor hallucis longus tendon. She resumed her professional activities within 2 months after endoscopic treatment.