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Peroneus Tertius Muscle

The peroneus tertius is a separated part of extensor digitorum longus, which shares its synovial sheath. It’s one of the muscles of the anterior compartment of the leg. The Peroneus tertius muscle is not always present.

The four muscles in the anterior compartment of the leg are the tibialis anterior, extensor digitorum longus, extensor hallucis longus, and peroneus tertius.

See Also: Anterior Compartment of Leg

Peroneus Tertius Muscle Anatomy

Proximally, the attachments and fleshy parts of the extensor digitorum longus and peroneus tertius are continuous; however, distally, the peroneus tertius tendon is separate and attaches to the 5th metatarsal, not to a phalanx. Although peroneus tertius contributes (weakly) to dorsiflexion, it also acts at the subtalar and transverse tarsal joints, contributing to eversion (pronation) of the foot.

It may play a special proprioceptive role in sensing sudden inversion and then contracting reflexively to protect the anterior tibiofibular ligament, the most commonly sprained ligament of the body.

Origin

The peroneus tertius arises with the extensor digitorum longus from the medial fibular shaft surface and the anterior intermuscular septum (between the extensor digitorum longus and the tibialis anterior).

Insertion

It inserts on the dorsal surface of the base of the fifth metatarsal.

See Also: Foot Anatomy

Innervation

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

Blood Supply

Its blood supply comes from the anterior tibial artery.

Action

Peroneus tertius muscle works with the extensor digitorum longus to dorsiflex, it also everts and abducts the foot.

Peroneus Tertius
OriginArises with the extensor digitorum longus from the medial fibular shaft surface and the anterior intermuscular septum (between the extensor digitorum longus and the tibialis anterior)
InsertionDorsal surface of the base of the fifth metatarsal
InnervationDeep peroneal nerve (L5, S1)
Blood SupplyAnterior tibial artery
ActionWorks with the extensor digitorum longus to dorsiflex,
Evert and abduct the foot

References & More

  1. Clinically Oriented Anatomy – 8th Edition
  2. Yammine K, Erić M. The Fibularis (Peroneus) Tertius Muscle in Humans: A Meta-Analysis of Anatomical Studies with Clinical and Evolutionary Implications. Biomed Res Int. 2017;2017:6021707. doi: 10.1155/2017/6021707. Epub 2017 May 17. PMID: 28596965; PMCID: PMC5449999. Pubmed
  3. Joshi SD, Joshi SS, Athavale SA. Morphology of peroneus tertius muscle. Clin Anat. 2006 Oct;19(7):611-4. doi: 10.1002/ca.20243. PMID: 16317742. Pubmed
Last Reviewed
December 29, 2023
Contributed by
OrthoFixar

Orthofixar does not endorse any treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice.

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