Peroneus tertius

The peroneus tertius (/ˌfɪbjᵿˈlɛərᵻs ˈtɛrʃi.əs/) (also known as fibularis tertius) is a muscle of the human body located in the lower limb.

The muscle arises from the lower third of the anterior surface of the fibula (anterior compartment of lower leg); from the lower part of the interosseous membrane; and from an intermuscular septum between it and the peroneus brevis muscle. The septum is sometimes called the intermuscular septum of Otto.