The tibialis anterior muscle is the large muscle on the outer front of the lower leg.
It extends from just below the knee down across the ankle and gets inserted into the bones of the feet.
There are four muscles in the anterior compartment of the lower leg; tibialis anterior, extensor digitorum longus, extensor hallucis longus and fibularis tertius.
Collectively, they act to dorsiflex (flex ankle towards the body) and invert the foot at the ankle joint.
The extensor digitorum longus and extensor hallucis longus also extend the toes. The muscles in this compartment are innervated by the deep fibular nerve (L4-L5), and blood is supplied via the anterior tibial artery.
The Tibialis anterior functions to stabilise the ankle, especially as the foot hits the ground during walking and running and as such pulls the foot off the ground into the air, to take the next step.
It is a powerful flexor muscle that moves the foot upwards (dorsiflexion) and twists it inwards (Inversion).