Leg and Foot Muscles: Anatomy and Function
Leg Muscles
1) Anterior Group
Innervation: Deep peroneal nerve, superficial peroneal nerve
A) Tibialis Anterior: Runs from the tibia to the inner edge of the foot. Its function is to dorsiflex and internally rotate the foot.
B) Extensor Hallucis Longus: Runs from the fibula to the second phalanx of the big toe. Its action is to extend the big toe and dorsiflex the foot on the leg while internally rotating it.
C) Extensor Digitorum Longus: Runs from the tibia and fibula to the last four toes. Its action is to extend the toes and dorsiflex the foot on the leg while externally rotating it.
D) Peroneus Tertius: An inconstant muscle. It originates and inserts on the tendon of the fifth toe.
2) External Side Group
A) Peroneus Brevis: Extends from the fibula to the fifth metatarsal. It abducts and externally rotates the foot.
B) Peroneus Longus: Extends from the tibia and fibula to the first metatarsal. Its action is to extend and externally rotate the foot, also increasing the plantar concavity.
3) Deep Posterior Group
Innervation: Tibial nerve
A) Popliteus: Attaches to the lateral condyle and the tibia. It externally rotates the flexed leg.
B) Flexor Digitorum Longus: Runs from the tibia to the plantar aspect of the last four toes. Its function is to flex the toes and extend the foot, tilting it inwards.
C) Tibialis Posterior: Runs from the tibia and fibula to the edge of the foot. Its function is to dorsiflex and internally rotate the foot.
D) Flexor Hallucis Longus: Extends from the fibula to the big toe. Its action is to flex the big toe.
4) Superficial Posterior Group
Innervation: Tibial nerve
A) Triceps Surae:
- a) Soleus: Extends from the fibula and tibia to the Achilles tendon.
- b) Gastrocnemius (Medial and Lateral Heads): Runs from the femoral condyles to the Achilles tendon.
Achilles Tendon: Forms a prominence in the back of the ankle. It is formed by the meeting of the three above-named muscles. This tendon inserts on the ankle, and its function is to extend the foot on the leg and to adduct and internally rotate the foot.
B) Plantaris: Runs from the lateral condyle to the heel bone. Its function is to assist the triceps surae.
Foot Muscles
1) Dorsal Region
Extensor Digitorum Brevis: A muscle that extends from the talus and calcaneus to the first four toes. Its action is an extensor of the phalanges.
Extensor Hallucis Brevis: Originates from the calcaneus and inserts into the proximal phalanx of the hallux. Its function is extension of the hallux.
2) Plantar Region
A) Dorsal Interossei: There are four dorsal interossei. They originate in the metatarsals and insert into the proximal phalanges. Their function is flexion of the first phalanx of the toes and abduction of the toes.
Plantar Interossei: They originate in the metatarsals and insert into the proximal phalanges. Their function is flexion of the first phalanx of the toes and adduction of the toes.
B) Quadratus Plantae: Originates from the calcaneus and goes to the long flexor tendon of the toes (last four).
C) Flexor Digitorum Brevis: Originates from the calcaneus and runs into the middle phalanx of toes two to four. Function: Flexion of toes two to four.
D) Flexor Hallucis Brevis: Has two parts. It arises from the cuneiform bones and inserts into the base of the proximal phalanx of the hallux. Function: Flexion of the big toe.
E) Abductor Hallucis: Originates from the calcaneus and inserts on the inner side of the base of the proximal phalanx of the hallux. Function: Abduction of the hallux.
Adductor Hallucis: Originates in the cuboid and the cuneiforms and inserts on the lateral side of the base of the proximal phalanx. Function: Adduction and flexion of the hallux.
F) Flexor Digiti Minimi Brevis: Arises from the base of the fifth metatarsal and inserts into the proximal phalanx of the fifth toe. Function: Abduction, flexion, and opposition of the fifth toe.
Abductor Digiti Minimi: Originates from the calcaneus and plantar fascia and inserts into the base of the proximal phalanx of the fifth toe and fifth metatarsal. Function: Abduction, flexion, and opposition of the fifth toe.
Opponens Digiti Minimi: Originates at the base of the fifth metacarpal and inserts into the lateral border of the fifth metacarpal. Function: Abduction, flexion, and opposition of the fifth toe.