Muscles Acting on the Foot and Ankle

Question 1

Extensor Digitorum Longus

Answer 1

Origin: lateral condyle of the tibia, anterior surface of the fibula, lateral portion of the interosseous membrane
Insertion: dorsum of the lateral 4 toes via extensor expansions (central slip inserts on base of middle phalanx, lateral slips on base of distal phalanx)
Action: extends the metatarsophalangeal, proximal interphalangeal and distal interphalangeal joints of the lateral 4 toes
Innervation: deep fibular (peroneal) nerve
Notes: one of the muscles involved in anterior compartment syndrome

Question 2

Extensor Hallucis Longus

Answer 2

Origin: middle half of the anterior surface of the fibula and the interosseous membrane
Insertion: base of the distal phalanx of the great toe
Action: extends the metatarsophalangeal interphalangeal joints of the great toe
Innervation: deep fibular (peroneal) nerve
Notes: one of the muscles involved in anterior compartment syndrome(Latin, hallex = great toe)

Question 3

Flexor Digitorum Longus

Answer 3

Origin: middle half of the posterior surface of the tibia
Insertion: bases of the distal phalanges of digits 2-5
Action: flexes the metatarsophalangeal, proximal interphalangeal and distal interphalangeal joints of digits 2-5; plantar flexes the foot
Innervation: tibial nerve
Notes: flexor digitorum longus in the leg is equivalent to the flexor digitorum profundus m. of the arm

Question 4

Flexor Hallucis Longus

Answer 4

Origin: lower 2/3 of the posterior surface of the fibula
Insertion: base of the distal phalanx of the great toe
Action: flexes the metatarsophalangeal and proximal interphalangeal joints of the great toe; plantar flexes the foot
Innervation: tibial nerve
Notes: flexor hallucis longus is very important in the “push off” part of the normal gait(Latin, hallex = great toe)

Question 5

Gastrocnemius

Answer 5

Origin: femur; medial head: above the medial femoral condyle; lateral head: above the lateral femoral condyle
Insertion: dorsum of the calcaneus via the calcaneal (Achilles’) tendon
Action: flexes leg; plantar flexes foot
Innervation: tibial nerve
Notes: the calcaneal tendon of the gastrocnemius and soleus is the thickest and strongest tendon in the body

Question 6

Fibularis (Peroneus) Brevis

Answer 6

Origin: lower one third of the lateral surface of the fibula
Insertion: tuberosity of the base of the 5th metatarsal
Action: extends (plantar flexes) and everts the foot
Innervation: superficial fibular (peroneal) nerve
Notes: stress fracture of the base of the 5th metatarsal bone is a common runner’s injury

Question 7

Fibularis (Peroneus) Longus

Answer 7

Origin: upper two/thirds of the lateral surface of the fibula
Insertion: after crossing the plantar surface of the foot deep to the intrinsic muscles, it inserts on the medial cuneiform and the base of the 1st metatarsal bone
Action: extends (plantar flexes) and everts the foot
Innervation: superficial fibular (peroneal) nerve
Notes: fibularis longus lies superficial to the fibularis brevis m. in the lateral compartment of the leg

Question 8

Fibularis (Peroneus) Tertius

Answer 8

Origin: distal part of the anterior surface of the fibula
Insertion: dorsum of the shaft of the 5th metatarsal bone
Action: everts the foot
Innervation: deep fibular (peroneal) nerve
Notes: fibularis tertius is in the anterior compartment of the leg, not the lateral compartment (which contains fibularis longus and brevis)

Question 9

Plantaris

Answer 9

Origin: above the lateral femoral condyle (above the lateral head of gastrocnemius)
Insertion: dorsum of the calcaneus medial to the calcaneal tendon
Action: flexes the leg; plantar flexes the foot
Innervation: tibial nerve
Notes: plantaris has a long slender tendon that is equivalent to the tendon of the palmaris longus m. of the arm; its tendon is often called the “freshman nerve” because it is often misidentified by the freshman medical student

Question 10

Soleus

Answer 10

Origin: posterior surface of head and upper shaft of the fibula, soleal line of the tibia
Insertion: dorsum of the calcaneus via the calcaneal (Achilles’) tendon
Action: plantar flexes the foot
Innervation: tibial nerve
Notes: soleus and the 2 heads of gastrocnemius are sometimes called the triceps surae muscle

Question 11

Tibialis Anterior

Answer 11

Origin: lateral tibial condyle and the upper lateral surface of the tibia
Insertion: medial surface of the medial cuneiform and the 1st metatarsal
Action: dorsiflexes and inverts the foot
Innervation: deep fibular (peroneal) nerve
Notes: acts as both an antagonist (dorsiflexion/plantar flexion) and a synergist (inversion) of the tibialis posterior m.

Question 12

Tibialis Posterior

Answer 12

Origin: interosseous membrane, posteromedial surface of the fibula, posterolateral surface of the tibia
Insertion: tuberosity of the navicular and medial cuneiform, metatarsals 2-4
Action: plantar flexes the foot; inverts the foot
Innervation: tibial nerve
Notes: acts as both an antagonist (dorsiflexion/plantar flexion) and a synergist (inversion) of the tibialis anterior m.