Origin: upper 2/3 of the lateral surface of the tibia and a narrow adjacent surface of the fibula and interosseous membrane.
Insertion: superficial at the distal end near the medial malleolus. Beneath the extensor retinacula, it crosses the medial border of the foot to reach its insertion at the inferior surface of the first cuneiform and first metatarsal bones
Action: primarily a strong invertor of the foot; helps in adduction, internal rotation and dorsi-flexion of the foot.
Extensor Digitorum Longus Muscle
Origin: upper 2/3 of the fibula and partly from the interosseous membrane.
Insertion: divides into 4 smaller tendons that are inserted to the middle and distal phalanges of the 4 lateral toes.
These are joined by the small tendons of the extensor digitorum brevis, interosseous and lumbrical muscles, which form fibrous extensions that surround the bones to which they are attached.
Origin: middle third of the fibula deep to the EDL.
Insertion: its slender tendon emerges between the tibialis anterior and EDL tendons. At the dorsum of the foot, it crosses medially to its insertion to the base of the distal phalanx of the big toe.
Peroneus Tertius Muscle – usually considered as a small slip of the EDL, which may be occasionally, present and distinguished by its fibers, which originate from the inferior third of the fibula. Its tendon may be mistaken as a 5th tendon of the EDL, but actually its tendon may be separated from the 4th or most lateral tendon of the EDL to its insertion at the tuberosity of the 5th metatarsal bone at the lateral border of the foot.
The neurovascular supply are located deep between the tibialis anterior and EDL muscles, bound by a common fascial sheath.
Anterior Tibial Artery – branches off from the popliteal artery at the inferior border of the popliteus muscle. It penetrates the upper end of the interosseous membrane to reach the anterior compartment where it descends vertically deep in the compartment on the anterior surface of the interosseous membrane down the ankle, where it surfaces beneath the superior extensor retinaculum between the tendons of the TA and EDL.
Name given to the continuation of the anterior tibial artery after crossing the lower border of the inferior extensor retinaculum. Its pulsations may be felt very well as it lies on the navicular and cuneiform bones.
It courses forwards on the dorsum of the foot and ends by dividing into:
A transversely directed “arcuate artery” that curves laterally at the bases of the metatarsal bones, distributing digital branches for the toes, to end at the lateral border of the foot by anastomosing with the lateral tarsal artery.
A “deep plantar artery” which perforates the first interosseous space to anastomose with the plantar arch at the sole of the foot.
2.2. It gives off lateral and medial tarsal branches that course deep to the tendons of the EDL, with anastomosing branches from the anterior tibial. Some branches reach the sole of the foot to communicate with branches from the plantar arteries.
2.3.A first dorsal metatarsal artery runs forwards to the first interosseous space, other dorsal metatarsal arteries for the interosseous spaces penetrate also to the sole and anastomose with plantar branches.
Accompanying veins drain into the anterior tibial vein, which joins the posterior tibial vein in the popliteal fossa to form the popliteal vein. Cutaneous veins unite to form a “dorsal venous arch” which is joined by veins from the hallux to form the long saphenous vein.
Muscle Origin Insertion Action Nerve Supply Tibialis anterior shaft of tibia and interosseous membrane medial cuneiform and base of first metatarsal extends the foot at ankle; inverts foot at subtalar and transverse tarsal joints helps to maintain the medial longitudinal arch of foot deep peroneal nerve Extensor digitorum longus shaft of fibula and interosseous membrane extensor expansion of lateral four toes extends toes; dorsiflexes (extends) foot deep peroneal nerve Peroneus tertius shaft of fibula and interosseous membrane base of fifth metatarsal dorsiflexes (extends) foot; everts foot at subtalar and transverse tarsal joints deep peroneal nerve
Extensor hallucis longus shaft of fibula and interosseous membrane base of distal phalanx of big toe extends big toe; dorsiflexes foot; inverts foot at subtalar and transverse tarsal joints deep peroneal nerve Extensor digitorum brevis calcaneus long extensor tendons to 2nd, 3rd, and 4th toes extends big toe deep peroneal nerve Extensor hallucis brevis calcaneus proximal phalanx of big tow extends big toe deep peroneal nerve
Muscle Origin Insertion Action Nerve Supply Peroneus longus shaft of fibula base of first metatarsal and the medial cuneiform plantar flexes (flexes) foot; everts foot at subtalar and transverse talar joints; supports lateral longitudinal arch and transverse arch of foot superficial peroneal nerve Peroneus brevis shaft of fibula base of fifth metatarsal bone plantar flexes (flexes) foot: everts foot at subtalar and transverse talar joints; holds up lateral longitudinal arch superficial peroneal nerve
Peroneus Longus – more superficial muscle of the two.
Origin: lateral surface of the upper half of the fibula.
Insertion: its tendon is covered by the peroneal retinaculum behind the lateral malleolus winds around the lateral border of the foot to enter the sole, crossing to the medial side to be inserted at the medial cuneiform and base of the first metatarsal.
Peroneus Brevis – deeper muscle covered by the longus.
Origin: lower half of the lateral surface of the fibula
Insertion: its short tendon deviates laterally to its attachment at the dorso-lateral surface of the 5th metatarsal at the lateral border of the foot, near but inferior to the insertion of the longus.
These two muscles, innervated by the “superficial peroneal (or musculo-cutaneous) nerve of the leg are the primary evertors of the foot, with concomitant abduction. They also help in the plantar flexion of the foot and support/maintain its arches.
Common Peroneal Nerve – given off in the popliteal fossa. It courses along the border of the biceps tendon to the neck of the fibula where it divides into:
Superficial Peroneal (Musculo-cutaneous Nerve of the Leg ), which enters the lateral compartment between the peroneal muscles, innervates them. At about the middle of the leg, it continues obliquely downwards and anteriorly, supplying cutaneous branches to the skin at the lower part of the leg and dorsum of the foot.
Deep Peroneal (Anterior tibial) Nerve – enters the anterior compartment after winding around the neck of the fibula. It is included in the fascial sheath of the anterior tibial vessels. After giving muscular branches to the muscles in the anterior compartment, it descends to the dorsum of the foot where it innervates the EDB, finally terminating as a cutaneous nerve to the skin between the first and second toes.