Extensor hallucis longus muscle
Extensor hallucis longus muscle is a thin muscle that extends from the middle third of fibula to the distal phalanx of the big toe (hallux). The muscle belongs to the anterior compartment of the leg together with three other muscles; extensor digitorum longus, tibialis anterior and fibularis tertius muscles.
Extensor hallucis longus is situated between tibialis anterior and extensor digitorum longus muscles. The muscle acts in three foot joints; talocrural, metatarsophalangeal and interphalangeal joints. The main action of extensor hallucis longus is to extend the big toe, but it has accessory actions in other joints as well.
|Origin||Middle third of medial surface of fibula, interosseous membrane|
|Insertion||Base of distal phalanx of great toe|
|Action||Metatarsophalangeal and interphalangeal joint 1: toe extension; talocrural joint: foot dorsiflexion|
|Innervation||Deep fibular nerve (L5, S1)|
|Blood supply||Anterior tibial artery|
In this article, we will discuss the anatomy and function of the extensor hallucis longus muscle.
Origin and insertion
Extensor hallucis longus muscle is situated in the anterior compartment of the leg. The muscle originates from the anteromedial aspect of fibula, lateral to the origin of tibialis anterior muscle and medial to extensor digitorum longus muscle. The origin of extensor hallucis longus extends to the anterior aspect of the interosseous membrane of the leg, located between fibula and tibia.
From here, the muscle runs inferomedially towards the foot, ending in a tendon. Passing through the dorsal aspect of the foot, and specifically deep to the superior extensor retinaculum and through the inferior extensor retinaculum, the tendon reaches its insertion point at the base and dorsal surface of the distal phalanx of the big toe. Prior to its insertion, the tendon of extensor hallucis gives off tendinous slips to the dorsal aspect of the first proximal phalanx and the first metatarsal.
Extensor hallucis longus is located between two muscles, posterolaterally to tibialis anterior and posteromedially to extensor digitorum longus muscle. The anterior tibial artery and vein and the deep peroneal nerve run between the extensor hallucis longus and the tibialis anterior muscles
The tendon of the muscle in the dorsum of the foot runs medially to the tendon of the extensor digitorum longus. Between those two tendons, the dorsalis pedis artery pulse can be easily palpated.
When extensor hallucis extends the big toe, the tendon of the muscle can be seen on the dorsal aspect of the big toe, laterally to the tendon of tibialis anterior muscle. The space between these two tendons is an important clinical location; it serves as an entry point for injections or aspiration procedures in the ankle joint.
Extensor hallucis longus is innervated by the deep fibular nerve (root value L5 and S1).
The blood supply for extensor hallucis longus mainly comes from the anterior tibial artery and its branches. In addition, the muscle can be supplied by the branches of fibular artery.
The venous blood from this compartment is mainly drained by anterior tibial vein which empties into popliteal vein.
Like the name suggests, the main function of extensor hallucis longus muscle is the extension of the big toe (hallux). This action happens in both metatarsophalangeal and interphalangeal joints of hallux. This extension is a crucial movement in walking and running.
Working together with other muscles from the anterior compartment of the leg, extensor hallucis longus muscle dorsiflexes the foot in the ankle joint. When the foot is fixed on the floor (e.g. walking or doing squats) the muscle pulls the body slightly forward and prevents losing gravity and falling backwards.
To expand your knowledge check out our video about the functions of extensor hallucis longus muscle and article and quiz about muscles of the leg.
Absent motor strength in the extensor hallucis longus muscle can occur due to muscle or nerve damage. Paralysis of extensor hallucis longus results in constant flexion of the big toe due to the unopposed action of the flexor muscles.
Considering the fact that extensor hallucis longus and its tendon run mostly superficially in the leg and dorsum of the foot, the muscle can easily be injured by dropping sharp objects in this region. The weakness or paralysis of this muscle can also indicate L5 nerve root damage, which is a common location for discus hernia.
It is important to mention the compartment syndrome which is a relatively common cause of the dysfunction of the extensor hallucis longus muscle. The compartment syndrome is a medical emergency caused usually by a blunt force trauma to the anterior aspect of the leg. Due to strong and inflexible fascial membranes, the swelling increases the pressure which compromises the circulation and function of the muscles (e.g. the extensor hallucis longus) within that space. The compartment syndrome requires an emergency surgical intervention.