The Peroneus Tertius Muscle

Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Peroneus tertius muscle

• The peroneus tertius muscle is absent in about 10% of the population.
• Located within the anterior compartment of the leg.
• Origin : from the distal third of the extensor surface of the fibula
• Insertion : into the base of 5th metatarsal bone
• Innervated by the deep peroneal nerve
• Function : Eversion and Dorsiflexion of the ankle
• Peroneus tertius muscle is used as a landmark when establishing the anterolateral portal of ankle arthroscopy. It is established just lateral to the peroneus tertius muscle and the superficial peroneal nerve, and medial to the lateral malleolus.
• One should attempt to look for and trace the superficial peroneal nerve before incision for the anterolateral portal.