Skip to content

Peroneus tertius



Fibularis tertius - anterolateral
Fibularis tertius - anterior

General information

  • The peroneus tertius is also called the fibularis tertius
  • 4-12% of the population do not have the peroneus tertius muscle


  • Mainly superficial


  • Anterior aspect of fibula
    • Distal 1/3
  • Membrana interossea
    • Distal 1/3


  • Base of 5 metatarsal
    • Dorsal surface

Main function

  • Ankle
    • Dorsiflexion
  • Tarsal joint
    • Eversion

Nerve innervation

  • Segmental
    • L5, S1
  • Peripheral
    • Deep part of peroneal nerve

Arterial supply

  • Anterior tibial artery

Palpation of the muscle belly

  • Patient position
    • Supine
  • Place your hand just medial to the lateral malleoli
  • Palpate just medially to the distal part of the shaft of the fibula just before the lateral malleolus

Palpation distal tendon

  • Patient position
    • Supine
  • Palpate the tendon of extensor digitorum longus that is attaching to the 5th toe
  • Ask the patient to give force towards eversion and dorsiflexion against your resistance so that the tendon of peroneus tertius becomes more visible