Extensor hallucis brevis: origin, insertion, action and innervation

The extensor hallucis brevis is a small muscle on the top of the foot that runs from the calcaneus to the base of the big toe. It extends the great toe at the metatarsophalangeal joint and is supplied by the lateral terminal branch of the deep fibular nerve (L5-S1).

Where it is

The extensor hallucis brevis is the most medial part of the short extensor mass on the dorsum of the foot. Many anatomists treat it as the first slip of the extensor digitorum brevis; Terminologia Anatomica lists it as a muscle of its own. Both muscles start together on the calcaneus, in front of the outer ankle, and fan out across the top of the foot.

Its belly runs obliquely, from the outer side of the dorsum toward the big toe, and its thin tendon crosses the first metatarsal. It lies lateral to the much thicker tendon of the extensor hallucis longus and runs next to it to the toe.

A useful landmark: the dorsalis pedis artery, whose pulse is felt on the top of the foot, usually passes just under (or alongside) the extensor hallucis brevis tendon on its way between the first and second metatarsals. See the underlying bones on bones of the foot.

Origin and insertion

• Origin: the upper surface of the front part of the calcaneus, sharing its origin with the extensor digitorum brevis.
• Insertion: the dorsal surface of the base of the proximal phalanx of the great toe, through a short tendon. It does not reach the distal phalanx.

That difference is the key to the muscle. The long extensor reaches the tip of the big toe; the short extensor stops at the base.

What it does

The extensor hallucis brevis extends the great toe at the metatarsophalangeal joint, the joint at the ball of the foot. It lifts the whole toe at its base, but it does not straighten the joint between the two phalanges of the big toe.

It works alongside the extensor hallucis longus. The long muscle is far stronger, lifts the tip of the toe as well and also dorsiflexes the ankle. The short muscle never crosses the ankle, so its only job is a direct pull at the base of the toe.

Innervation and blood supply

The extensor hallucis brevis is supplied by the lateral terminal branch of the deep fibular nerve (L5-S1), the same branch that supplies the extensor digitorum brevis. The medial terminal branch of the deep fibular nerve does not supply muscle on the dorsum: it carries sensation from the web of skin between the first and second toes.

Its blood comes from the dorsalis pedis artery, mainly through its lateral tarsal branch.

How to remember it

• "Brevis stops at the base": the short extensor of the big toe inserts on the proximal phalanx; the long one goes on to the distal phalanx.
• Big-toe slip of the short extensor: learn the extensor digitorum brevis and add its first slip to the big toe, and you have learned this muscle too.
• Lateral branch for both short extensors: the deep fibular nerve's lateral branch serves the whole short extensor mass.
• Crosses the pulse: on the dorsum, its small tendon crosses over the dorsalis pedis artery.

Test yourself in the leg and foot quiz.

Frequently asked questions

What does the extensor hallucis brevis do?

It extends the great toe at the metatarsophalangeal joint.

What nerve supplies the extensor hallucis brevis?

The lateral terminal branch of the deep fibular nerve, from roots L5 and S1.

Where does the extensor hallucis brevis insert?

On the dorsal surface of the base of the proximal phalanx of the great toe.

Is the extensor hallucis brevis part of the extensor digitorum brevis?

It is often described as the medial part of that muscle, since both share one origin and one nerve, but it is usually named separately.

Sources

• OpenStax, Anatomy and Physiology 2e, 11.6 Appendicular muscles of the pelvic girdle and lower limbs
• OpenStax, Anatomy and Physiology 2e, 8.4 Bones of the lower limb
• Z-Anatomy, the libre 3D atlas of anatomy