Overview
The musculature of the lower leg is divided into anterior, lateral (fibular), posterior (superficial and deep) compartments, defined by intermuscular septa. Collectively, they act to dorsiflex and invert the foot at the ankle joint.
Arterial Supply
Blood is supplied via the anterior tibial artery
Tibialis Anterior
The tibialis anterior muscle is located alongside the lateral surface of the tibia and is the strongest dorsiflexor of the foot.
- Attachments: Originates from the lateral tibial condyle, proximal half of the tibial shaft and interosseous membrane
- Course: Tendon travels medially, passing under the superior (transcrural) and inferior (cruciate) extensor retinaculum of the ankle
- Insertion: Attaches to the medial cuneiform and the base of the first metatarsal
- Actions: Dorsiflexion and inversion of the foot at the ankle (talocrural) joint
- Innervation: Deep fibular (peroneal) nerve (L4, L5) – small terminal branch of the sciatic nerve
- Relations:
- Medial to the anterior tibial artery and deep fibular nerve
Extensor Digitorum Longus
The extensor digitorum longus lies lateral and deep to the tibialis anterior. The tendons of the EDL can be palpated on the dorsal surface of the foot.
- Origin: Originates from the lateral condyle of the tibia and the medial surface of the fibula.
- Insertion: The fibres converge into a tendon, which travels to the dorsal surface of the foot. The tendon splits into four, each inserting onto a toe.
- Actions: Extension of the lateral four toes, and dorsiflexion of the foot.
- Innervation: Deep fibular (peroneal) nerve (L4, L5) – small terminal branch of the sciatic nerve
Extensor Hallucis Longus
The extensor hallucis longus is located deep to the EDL and TA.
- Origin: Originates from the medial surface of the fibular shaft
- Insertion: The tendon crosses anterior to the ankle joint and attaches to the base of the distal phalanx of the great toe
- Action: Extension of the great toe and dorsiflexion of the foot
- Innervation: Deep fibular (peroneal) nerve (L4, L5) – small terminal branch of the sciatic nerve
Fibularis Tertius
The fibularis (peroneal) tertius muscles arises from the most inferior part of the extensor digitorum longus
- Origin: Originates with the extensor digitorum longus from the medial surface of the fibula.
- Insertion: The tendon descends with the EDL, until they reach the dorsal surface of the foot. The fibularis tertius tendon then diverges and attaches to the 5th metatarsal
- Actions: Eversion and dorsiflexion of the foot.
- Innervation: Deep fibular (peroneal) nerve (L4, L5) – small terminal branch of the sciatic nerve
Variants
- Absence of fibularis (peroneal) tertius