Anterior compartment

Tibialis anterior: Acts as the primary dorsiflexor and inverter of the foot, inserting into the medial cuneiform and first metatarsal base. Crucial for toe clearance during the swing phase of the gait cycle. Originates as the most medial muscle of the anterior compartment, arising immediately lateral to the tibial tuberosity and tibial crest.

Extensor digitorum longus (EDL): Originates from the lateral proximal tibia - directly anterior to the fibula head. Distally, it forms a tendon which passes beneath the superior and inferior extensor retinaculi lateral to EHL, before dividing into four tendons which each insert to the distal phalanx of the 2nd to 5th toes.

Extensor hallucis longus (EHL): Originates beneath the other anterior compartment muscles from the middle third of the fibula and interosseous membrane. As it passes beneath the extensor retinaculum, it crosses above the anterior tibial artery as it transitions to become the dorsalis pedis.

Peroneus tertius: Inserts into the metaphysis of the 5th metatarsal base to evert the foot. As a small muscle (which is absent in 10-15% of individuals), it is felt to play a more important role in ankle proprioception than power/strength.

Lateral compartment:

Peroneus longus: Originates from the head/neck of the fibula, with the common peroneal nerve winding around the fibula neck immediately below the peroneus longus origin (known as the peroneal tunnel). After passing behind the lateral malleolus, the tendon winds beneath the midfoot to enter the peroneal sulcus of the cuboid bone. It inserts into the medial cuneiform and the base of the 1st metatarsal, acting as a direct antagonist to tibialis anterior to cause eversion and plantarflexion. As it crosses beneath the midfoot, it acts an important dynamic structure of the lateral longitudinal and transverse arches.

Peroneus brevis: Originates frm the distal half of the fibula, and passes beneath the lateral malleolus as the tendon in closest relation to bone within the retromalleolar groove. It inserts into the base of the 5th metatarsal, where it everts the foot. Avulsion of this tuberosity is known as a pseudo-Jones fracture.

Superficial posterior compartment:

Gastrocnemius: Powerful plantarflexor of the ankle; with some additional flexion activity at the knee. Two heads originate from the medial and lateral femoral condyles and merge distally with the fibres of soleus to form the Achilles tendon.

Soleus: Plantarflexes the ankle independently of knee position. Originates from the posterior tibia and fibula below the soleal line. Rich in Type I slow-twitch muscle fibres and acts as a major stabiliser in postural control. Combined with gastrocnemius, the two muscles are known as the triceps surae and insert on the calcaneus via the Achilles tendon.

Plantaris: Vestigial muscle which is absent in ~10% of individuals. It originates from the lateral supracondylar line of the femur and inserts variably on the calcaneus or merges with the Achilles tendon.

Deep posterior compartment:

Tibialis posterior: Originates from the lateral aspect of the posterior tibia and interosseous membrane. It’s tendon passes through the tarsal tunnel beneath the medial malleolus before spreading out to a broad insertion across the underside of the navicular bone, medial/intermediate cuneiforms and 2nd-4th metatarsal bases. As it passes underneath the medial side of the midfoot, it passes beneath and reinforces the spring ligament, playing a major role as a dynamic support of the medial arch.