Name

# Peroneus Tertius

Pronunciation

(per-o-NE-us TER-shus)

Origin/Proximal Attachment

Distal 3rd or more of the medial surface of the fibula

Adjoining surface of the interosseus membrane

Anterior crural intermuscular septum

Insertion/Distal Attachment

Medial part of dorsal surface of the base of the 5th metatarsal bone

(A thin expansion usually extends forwards along the medial border of the shaft of the bone)

Action/Relevance

With extensor digitorum longus & tibialis anterior produce dorsiflexion & eversion of the foot

Innervation

Part of extensor digitorum longus

Tendon passes behind the superior extensor retinaculum & within the loop of the inferior extensor retinaculum that it shares with extensor digitorum longus

Notes

Peroneus tertius is one of the muscles of the anterior crural compartment of the leg. It is sometimes considered as an accessory part of extensor digitorum longus.

It originates from the inferior third of the anterior surface of the fibula and the adjoining interosseous membrane. It passes distally in the company of extensor digitorum longus under the superior and then the inferior extensor retinaculum. It inserts into the base and shaft of the dorsal fifth metatarsal.

It is innervated by the deep peroneal nerve (L5,S1).

Peroneus tertius acts to dorsiflex and evert the foot.