Intrinsic Foot and Toe Muscles

Question 1

Abductor Digiti Minimi (Foot)

Answer 1

Origin: medial and lateral sides of the tuberosity of the calcaneus
Insertion: lateral side of the base of the proximal phalanx of the 5th digit
Action: abducts the 5th toe; flexes the metatarsophalangeal joint
Innervation: lateral plantar nerve
Notes: abductor digiti minimi forms the lateral margin of the sole of the foot

Question 2

Abductor Hallucis

Answer 2

Origin: medial side of the tuberosity of calcaneus
Insertion: medial side of the base of the proximal phalanx of the great toe (hallux)
Action: abducts the great toe; flexes the metatarsophalangeal joint
Innervation: medial plantar nerve
Notes: abductor hallucis forms the medial margin of the sole of the foot(Latin, hallex = great toe)

Question 3

Adductor Hallucis

Answer 3

Origin: oblique head: bases of metatarsals 2-4; transverse head: heads of metatarsals 3-5
Insertion: lateral side of base of the proximal phalanx of the great toe
Action: adducts the great toe (moves it toward midline of the foot; i.e.toward the 2nd digit)
Innervation: deep branch of the lateral plantar nerve
Notes: the plantar arterial arch passes superior to the oblique head of adductor hallucis(Latin, hallex = great toe)

Question 4

Flexor Digiti Minimi Brevis (Foot)

Answer 4

Origin: base of 5th metatarsal bone
Insertion: lateral side of base of proximal phalanx of 5th digit
Action: flexes the metatarsophalangeal joint of the 5th digit
Innervation: lateral plantar nerve
Notes: none

Question 5

Flexor Digitorum Brevis

Answer 5

Origin: tuberosity of the calcaneus, plantar aponeurosis, intermuscular septae
Insertion: base of the middle phalanx of digits 2-5 after splitting to allow passage of the flexor digitorum longus tendons
Action: flexes the metatarsophalangeal & proximal interphalangeal joints of digits 2-5
Innervation: medial plantar nerve
Notes: flexor digitorum brevis in the foot is equivalent to the flexor digitorum superficialis m. of the arm

Question 6

Flexor Hallucis Brevis

Answer 6

Origin: cuboid, lateral cuneiform, medial side of the first metatarsal
Insertion: medial belly: medial side of proximal phalanx of the great toe; lateral belly: lateral side of the proximal phalanx of the great toe
Action: flexes the metatarsophalangeal joint of the great toe
Innervation: medial plantar nerve (lateral belly occasionally receives innervation from the lateral plantar nerve)
Notes: each tendon of insertion contains a sesamoid bone(Latin, hallex = great toe)

Question 7

Interosseous, Dorsal (Foot)

Answer 7

Origin: shafts of adjacent metatarsal bones
Insertion: bases of the proximal phalanges for digit 2 (both sides) & digits 3,4 (lateral side)
Action: abduct digits 2-4 (move these digits away from midline as defined by a plane passing through the 2nd digit); flex the metatarsophalangeal joints and extend the interphalangeal joints of those digits
Innervation: deep branch of the lateral plantar nerve
Notes: four in number; remember DAB (Dorsal interossei ABduct) and PAD (Plantar interossei ADduct), then logic can tell you where these muscles insert(Latin, inter = between + os = bone)

Question 8

Interosseous, Plantar

Answer 8

Origin: base and medial side of metatarsals 3-5
Insertion: bases of proximal phalanges and extensor expansions of digits 3-5
Action: adduct digits 3-5 (move these digits toward the midline of the foot as defined by a plane through the second digit); flex the metacarpophalangeal and extend interphalangeal joints of digits 3-5
Innervation: deep branch of the lateral plantar nerve
Notes: remember PAD (Plantar interossei ADduct) and DAB (Dorsal interossei ABduct), and logic will tell you where these muscles must insert(Latin, inter = between + os = bone)

Question 9

Lumbricals (Foot)

Answer 9

Origin: tendons of the flexor digitorum longus
Insertion: medial side of the extensor expansion of digits 2-5
Action: flex the metatarsophalangeal joint, extend the proximal interphalangeal & distal interphalangeal joints of digits 2-5
Innervation: medial (1st) lumbrical: medial plantar nerve; lateral three lumbricals: lateral plantar nerve
Notes: the lumbricals of the foot have the same action on the toes that the lumbricals in the hand have on the fingers(Latin, lumbricus = earthworm)

Question 10

Quadratus Plantae

Answer 10

Origin: anterior portion of the calcaneus and the long plantar ligament
Insertion: tendons of the flexor digitorum longus m.
Action: assists the flexor digitorum longus in flexing the toes
Innervation: lateral plantar nerve
Notes: the quadratus plantae m. changes the line of force of the flexor digitorum longus m. to bring it in line with the long axis of the foot(Latin, quadratus = square)