Author: Dr Peter de Souza
Last modified: 18 November 2022

The peroneus tertius (fibularis tertius) is one of the muscles within the anterior compartment of the leg. Collectively, the muscles of the anterior compartment act to extend the toes, dorsiflex the ankle and invert the foot.

The leg is comprised of anterior, lateral and posterior compartments.

The anterior compartment consists of four muscles:

  • Tibialis anterior
  • Extensor hallucis longus
  • Extensor digitorum longus
  • Fibularis/peroneus tertius


  • Distal part of medial fibula


  • Dorsomedial surface of base of 5th metatarsal


  • Dorsiflexion of foot
  • Eversion of foot


  • Deep fibular nerve: L5,S1

Blood Supply

  • Anterior tibial artery