Tibialis anterior muscle

At a glance

English

Tibialis anterior muscle

Latin (TA2)

Musculus tibialis anterior

System

Muscle

Region

Lower limb

Side

Paired, left and right

Inserts on

The first metatarsal bone

About the tibialis anterior muscle

Of the muscles in the front compartment of the leg, tibialis anterior is the biggest and lies furthest medially. It lies just lateral to the sharp front border of the tibia, so its fleshy upper part and its tendon in front of the ankle are easy to see and feel when the foot is pulled up. It is thick and muscular above and becomes tendinous in the lower third of the leg.

It arises from the lateral condyle and from the lateral surface of the tibial shaft over its upper two-thirds, from the neighbouring interosseous membrane, from the deep fascia over it and from the septum between it and extensor digitorum longus. Its fibres run down to a tendon that passes under the superior and inferior extensor retinacula in their most medial channel, enclosed in its own synovial sheath. It crosses the front of the ankle and inserts on the medial and plantar surfaces of the medial cuneiform and the neighbouring first metatarsal base. In the upper leg it covers the anterior tibial vessels together with the deep fibular nerve, which lie on the interosseous membrane beside it.

The muscle dorsiflexes the ankle and inverts the foot, and it is the strongest dorsiflexor. In walking it works twice in every step: just after heel strike it lengthens under control to lower the forefoot gently to the ground, and during swing it shortens to lift the toes clear. With the foot planted, it helps balance the leg over the foot on uneven ground. It works with tibialis posterior in inversion but against it in movement at the ankle, while fibularis longus, which everts the foot and lowers the first ray, is its closest opponent. The calf muscles oppose its dorsiflexion.

Its nerve is the deep fibular nerve, a branch of the common fibular nerve, and by the anterior tibial artery. Damage to the common fibular nerve at the neck of the fibula paralyses it, producing foot drop and a high-stepping gait. Overuse can cause pain along its line of origin, one form of shin splints, and swelling within the tight anterior compartment can lead to a compartment syndrome.

Attachments, action and supply

Origin

Lateral condyle and upper two-thirds of the tibia's lateral surface, the interosseous membrane, the overlying fascia and the septum with extensor digitorum longus.

Insertion

Medial and plantar surfaces of the medial cuneiform and the first metatarsal base.

Action

Dorsiflexes the ankle and inverts the foot; controls lowering of the foot after heel strike.

Nerve supply

Deep fibular nerve (L4, L5).

Blood supply

Anterior tibial artery.