The anterior compartment of the leg contains four muscles that mainly dorsiflex the foot (lift it upward) and help with inversion (turning the sole inward).
These muscles are supplied by the deep fibular nerve (L4–S2).

The four muscles are:

• Tibialis anterior

• Extensor hallucis longus

• Extensor digitorum longus

• Fibularis tertius.

The shared function of these muscles is related to how they attach: they arise from the tibia or fibula and cross the front of the ankle to insert onto bones on the top of the foot or toes. When they contract, they shorten and pull the foot upward.

Tibialis Anterior

The tibialis anterior is the largest and strongest muscle in this compartment. It lies directly beside the lateral edge of the tibia and is easily felt when you dorsiflex your foot.  

The tibialis anterior dorsiflexes the foot at the ankle (main dorsiflexor), inverts the foot at the subtalar joint (turns sole inward), and helps support the medial longitudinal arch (important for balance and walking).

Tibialis anterior is especially active when walking downhill, during the swing phase of gait, and when controlling foot placement on the ground.

• Origin: Lateral tibial condyle, upper half of the lateral tibial shaft, and interosseous membrane.

• Insertion: Medial cuneiform and base of the first metatarsal.

• Innervation: Deep fibular nerve.

Extensor Hallucis Longus

The extensor hallucis longus is a long, thin muscle located between the tibialis anterior and extensor digitorum longus.

It extends the big toe - especially important when lifting your foot off the ground while walking and dorsiflexes the foot.

Its tendon appears on the top of the foot as a distinct cord leading to the big toe.

• Origin: Middle third of the medial surface of the fibula and interosseous membrane.

• Insertion: Base of the distal phalanx of the big toe.

• Innervation: Deep fibular nerve.

Extensor Digitorum Longus

The extensor digitorum longus lies laterally and is the most posterior muscle in the anterior compartment.

It extends toes 2–5, dorsiflexes the foot, and has a slight contribution to inversion.

At the top of the foot, the four tendons are easy to see when the toes are extended.

• Origin: Lateral condyle of the tibia, upper half of the medial fibula, and interosseous membrane.

• Insertion: Splits into four tendons that attach to the middle and distal phalanges of toes 2–5.

• Innervation: Deep fibular nerve.

Fibularis Tertius

The fibularis (peroneus) tertius is considered a part of the extensor digitorum longus muscle because it branches off from its lower portion. Not everyone has this muscle.

It dorsiflexes the foot and everts the foot (turns the sole outward).

• Origin: Lower third of the medial fibula.

• Insertion: Dorsal surface of the base of the fifth metatarsal.

• Innervation: Deep fibular nerve.

This muscle helps stabilize the foot during walking, especially during sudden directional changes.

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