Fibularis Tertius

Joe Muscolino

Share This

The fibularis tertius muscle of the anterior compartment of the (lower) leg.

The Fibularis Tertius is located in the Anterior Compartment of the (lower) leg. The muscles in the anterior compartment are:



  • Distal anterior fibula to the base of the fifth metatarsal.
    • The fibularis tertius attaches proximally onto the distal 1/3 of the anterior fibula and distal 1/3 of the interosseus membrane.
    • The fibularis tertius attaches distally onto the dorsal surface of the base of the fifth metatarsal.



  • Dorsiflexes the foot at the ankle joint.
  • Everts (Pronates) the foot at the subtalar joint.



  1. The fibularis tertius is actually structurally part of the extensor digitorum longus. It has been separated from the extensor digitorum longus because it attaches onto a metatarsal, not a “digit”, i.e., not a phalanx.
  2. The fibularis tertius used to be named the peroneus tertius; it was renamed at an Anatomy Congress in 1999.
  3. Eversion is the principal cardinal-plane (frontal-plane) component of the oblique-plane motion pattern of pronation.