Peroneus tertius

The peroneus tertius (also known as fibularis tertius) is a muscle of the human body located in the lower limb. It does not exist in all individuals.

The peroneus tertius is a part of the extensor digitorum longus, and might be described as its fifth tendon.

The fibers belonging to this tendon arise from the lower third or more of the anterior surface of the fibula; from the lower part of the interosseous membrane; and from an intermuscular septum between it and the peroneus brevis.

The tendon, after passing under the transverse and cruciate crural ligaments in the same canal as the extensor digitorum longus, is inserted into the dorsal surface of the base of the metatarsal bone of the little toe (5th metatarsal).