Extensor hallucis longus: origin, insertion, action and innervation

The extensor hallucis longus is a thin muscle in the front of the leg whose tendon runs over the top of the foot to the tip of the big toe. It extends the great toe at both of its joints, helps dorsiflex the ankle, and is supplied by the deep fibular nerve (L5-S1).

Where it is

The extensor hallucis longus lies in the anterior compartment of the leg. In the upper part of the leg it is hidden, buried between the tibialis anterior on the inner side and the extensor digitorum longus on the outer side. Only in the lower third does it come to the surface between them.

Its tendon crosses the front of the ankle under the extensor retinacula, lateral to the tibialis anterior tendon. On the top of the foot, it runs along the first metatarsal to the big toe. Pull your big toe up hard and you can see this tendon as a sharp cord on the inner side of the dorsum of the foot.

The anterior tibial artery and the deep fibular nerve run down the leg close to this muscle. At the ankle, the artery becomes the dorsalis pedis artery, whose pulse is felt just lateral to the extensor hallucis longus tendon on top of the foot. See the anterior compartment on muscles of the leg.

Origin and insertion

• Origin: the middle part of the medial (front) surface of the fibula and the neighboring interosseous membrane.
• Insertion: the dorsal surface of the base of the distal phalanx of the great toe. A slip often also reaches the base of the proximal phalanx.

So the tendon runs the full length of the big toe, which is why it can lift the toe tip as well as the base.

What it does

1. Extension of the great toe: it lifts the big toe at the metatarsophalangeal joint and straightens it at the interphalangeal joint.
2. Dorsiflexion of the ankle: it crosses the front of the ankle, so it helps raise the foot, together with the tibialis anterior and the extensor digitorum longus.

During the swing phase of walking it holds the big toe up so it does not catch on the ground. Lifting the big toe against a finger is a common bedside test of the L5 nerve root.

Innervation and blood supply

The extensor hallucis longus is supplied by the deep fibular nerve (L5-S1), which supplies all the muscles of the anterior compartment. The nerve runs down beside the muscle on the interosseous membrane.

Its blood comes from the anterior tibial artery.

How to remember it

• Two toe joints plus the ankle: the long extensor lifts the big toe at both of its joints and also helps lift the foot.
• Hidden at the top, visible at the bottom: it is covered by its neighbors in the upper leg and appears between them near the ankle.
• Big toe up, find the tendon, find the pulse: the dorsalis pedis pulse lies just lateral to the tendon.
• Middle of the three tendons: at the front of the ankle, the extensor hallucis longus tendon sits between the tibialis anterior (medial) and the extensor digitorum longus (lateral).

Test yourself in the leg and foot quiz.

Frequently asked questions

What does the extensor hallucis longus do?

It extends the big toe at the metatarsophalangeal and interphalangeal joints and helps dorsiflex the ankle.

What nerve supplies the extensor hallucis longus?

The deep fibular nerve, from roots L5 and S1.

Where does the extensor hallucis longus insert?

On the base of the distal phalanx of the great toe, on its upper surface.

Where is the extensor hallucis longus tendon on the foot?

On the inner side of the top of the foot, running along the first metatarsal to the big toe. You can see it when you lift the big toe.

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