The muscles acting on the foot can be divided into two distinct groups; extrinsic and intrinsic muscles.
- Extrinsic muscles arise from the anterior, posterior and lateral compartments of the leg. They are mainly responsible for actions such as eversion, inversion, plantarflexion and dorsiflexion of the foot.
- Intrinsic muscles are located within the foot and are responsible for the fine motor actions of the foot, for example movement of individual digits.
In this article, we shall examine the anatomy of the intrinsic muscles of the foot. They can be divided into those situated on the dorsum of the foot, and those in the sole of the foot.
Dorsal Aspect
There are two intrinsic muscles located within the dorsum of the foot – the extensor digitorum brevis and extensor hallucis brevis.
They assist the extrinsic muscles of the foot in extending the toes and are both innervated by the deep fibular nerve.
Extensor Digitorum Brevis
The extensor digitorum brevis is a small, thin muscle which lies underneath the long extensor tendons of the foot.
- Attachments: Originates from the calcaneus and inferior extensor retinaculum. It attaches onto the long extensor tendons of the medial four toes.
- Actions: Extension of the lateral four toes.
- Innervation: Deep fibular nerve.
Extensor Hallucis Brevis
The extensor hallucis brevis is often considered to be the medial part of the extensor digitorum brevis muscle, rather than a separate structure.
- Attachments: Originates from the calcaneus and inferior extensor retinaculum. It attaches to the base of the proximal phalanx of the great toe.
- Actions: Extension of the great toe.
- Innervation: Deep fibular nerve.
By TeachMeSeries Ltd (2023)
