The extensor hallucis longus (EHL) is a slender muscle in the lower leg that plays a specific role in foot and toe movement. Its actions are particularly noticeable in movements involving the big toe and overall foot positioning.
Anatomy and Position
The extensor hallucis longus (EHL) muscle resides in the anterior compartment of the lower leg, positioned between the tibialis anterior and extensor digitorum longus muscles. It originates from the middle portion of the fibula and the adjacent interosseous membrane.
From its origin, the muscle fibers form a long tendon that passes along the front of the ankle and foot. This tendon travels underneath the superior and inferior extensor retinacula, which hold tendons in place. It then inserts onto the dorsal surface (top) of the base of the distal phalanx of the great toe.
The deep fibular nerve, also known as the deep peroneal nerve, innervates the extensor hallucis longus muscle, controlling its contractions. Blood supply to the EHL comes primarily from the anterior tibial artery.
How the Muscle Moves the Foot and Toe
The primary action of the extensor hallucis longus is to extend the great toe, meaning it lifts the big toe upwards. This movement occurs at both the metatarsophalangeal joint (where the toe meets the foot) and the interphalangeal joint (within the toe itself). When the muscle contracts, its tendon pulls on the distal phalanx, causing the big toe to extend.
The EHL also has a secondary action, assisting in dorsiflexion of the ankle. Dorsiflexion refers to the movement that brings the top of the foot upwards, closer to the shin. This action occurs as the muscle shortens, pulling the entire foot upwards at the ankle joint. While not its main role, this contribution to ankle dorsiflexion is important for overall foot mechanics.
When the extensor hallucis longus contracts, it shortens, pulling its insertion point (the big toe’s distal phalanx) closer to its origin (the fibula and interosseous membrane). This pulling force translates into the lifting movements of the big toe and, to a lesser extent, the entire foot. The muscle works in coordination with other muscles in the anterior compartment of the leg to achieve these movements.
Its Role in Daily Activities
The actions of the extensor hallucis longus are integral to many everyday movements, particularly during walking and maintaining stability. During the swing phase of walking, when the foot is lifted off the ground, the EHL actively lifts the big toe to prevent it from dragging. This toe clearance is important for avoiding trips and falls. Without this lifting action, the front of the foot, especially the big toe, would frequently catch on the ground.
The muscle’s contribution to ankle dorsiflexion also supports the foot’s ability to clear the ground during locomotion. This combined action of lifting the big toe and assisting with foot dorsiflexion ensures a smooth and efficient gait. It also helps in controlling the descent of the foot after heel strike, preventing the foot from slapping down abruptly.
Beyond walking, the extensor hallucis longus contributes to balance, whether a person is standing still or engaged in physical activities. Its ability to stabilize the ankle and foot helps maintain proper posture and control during various movements. If the EHL’s function is compromised, individuals might experience difficulty with activities requiring precise foot control, such as climbing stairs or pulling on socks, as the big toe may tend to fold under the foot.