MSK Muscles of the foot

Question 1

Name the muscles on the dorsal and plantar aspect of the foot

Answer 1

Dorsal aspect:
Extensor digitorum brevis
Extensor hallucis brevis

Plantar aspect:
1st layer (most superficial) Adductor hallucis, flexor digitorum brevis, abductor digiti minimi
2nd layer quadratus plantae, lumbricals
3rd layer flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis
4th layer (deepest) plantar interossei, dorsal interossei

Question 2

Dorsal aspect

What are the attachments and actions of the extensor digitorum brevis?

Answer 2

Lies deep to tendon for extensor digitorum longus

Originates from calcaneus, interosseous talocalcaneal ligament and inferior extensor retinaculum
Attaches to long extensor tendons of the 2 digits

Actions:
aids extensor digitorum longus in extending toes at MTP and IP joints

Question 3

Dorsal aspect

What are the attachments and actions of the extensor hallucis brevis?

Answer 3

Medial to extensor digitorum longus and lateral to extensor hallucis longus

Originates from calcaneus, interossei talocalcaneal ligament and inferior extensor retinaculum
Attaches to base of phalanx of great toe

Actions:
Aids extensor hallucis longus in extension of great toe and MTP joint

Question 4

1st layer

What are the attachments and actions of the adductor hallucis?

Answer 4

Medial side of sole

Originates from medial calcaneus, flexor retinaculum and plantar aponeurosis. Attaches to medial base of proximal phalanx of great toe

Actions:
Abducts and flexes great toe

Question 5

What is the innervation of the muscles of the dorsal surface of the foot?

Answer 5

The deep fibular nerve

Question 6

1st layer

What are the attachments and actions of the flexor digitorum brevis?

Answer 6

Lateral to adductor hallucis

Originates from medial calcaneus and plantar aponeurosis. Attaches to middle phalanges of four digits

Actions:
Flexes 4 digits at proximal IP joints

Question 7

1st layer

What are the attachments and actions of the abductor digiti minimi?

Answer 7

Originates from medial and lateral tubercles of calcaneus and the plantar aponeurosis. Attaches to lateral base of proximal phalanx of little toe

Actions:
Abducts and flexes 5th digit

Question 8

2nd layer

What are the attachments and actions of the quadratus plantae?

Answer 8

Superior to flexor digitorum longus tendons

Originates from medial lateral and plantar surface of calcaneus. Attaches to tendons of flexor digitorum longus

Actions:
assists flexor digitorum longus in flexing lateral 4 digits

Question 9

2nd layer

What are the attachments and actions of the lumbricals?

Answer 9

There are 4 lumbricals - they are eacg medial to their respective tendon of the flexor digitorum longus

Originate from tendons of flexor digitorum longus and attach to extensor hoods of 4 digits

Actions:
Flex MTP joints and extend IP joints

Question 10

3rd layer

What are the attachments and actions of the flexor hallucis brevis?

Answer 10

Medial side of foot

Originates from plantar surface of cuboid + lat cuneiform, and from the posterior tibialis tendon. Attaches to base of proximal phalanx of great toe

Actions:
Flexes great toe at MTP joint

Question 11

3rd layer

What are the attachments and actions of the adducor hallucis?

Answer 11

Located laterally to flexor hallucis brevis

Originates from bases of first 4 metatarsals and plantar ligaments of the MTP joints. Attaches to lateral base of proximal phalanx of toe

Actions:
Adducts great toe

Question 12

3rd layer

What are the attachments and actions of the flexor digiti minimi brevis?

Answer 12

Located under the metatarsal of the little toe

Originates from of base of 5th metatarsal and attaches to base of proximal phalanx of little toe

Actions:
Flexes proximal phalanx of little toe

Question 13

4th layer

What are the attachments and actions of the plantar interossei?

Answer 13

Plantar interossei are unipennate (each originate from a single metatarsal)
There are 3 of them

Originate from medial side of metatarsals 3 4 5
Attaches to medial phalanges of digits 3 4 5

Actions:
adduct and flex MTP joints of digits 3 4 5

Question 14

4th layer

What are the attachments and actions of the dorsal interossei?

Answer 14

Dorsal interossei are bipennate (originate from 2 metatarsals)
There are 4 of them

Originate from sides of metatarsals 1-5
The first muscle attaches to medial side of proximal phalanx of second digit
Interossei 2 3 and 4 attach to lateral sides of phalax of digits 2 3 and 4 (basically the index finger has 2)

Actions:
Abducts and flexes MTP joint of digits 2 3 and 4

Question 15

What is the innervation of the muscles in the 1st layer of plantar aspect of the foot?

Answer 15

Adductor hallucis and flexor digitorum brevis - medial plantar nerve

Adductor digiti minim - lateral plantar nerve

Question 16

What is the innervation of the muscles in the 2nd layer of plantar aspect of the foot?

Answer 16

Quadratus plantae and 3 lateral lumbricals - lateral plantar nerve
Most medial lumbrical - medial plantar nerve

Question 17

What is the innervation of the muscles in the 3rd layer of plantar aspect of the foot?

Answer 17

Flexor hallucis brevis - medial plantar nerve
adductor hallucis - deep branch of lateral plantar nerve
Flexor digiti minimi brevis - superficial branch of lateral plantar nerve

Question 18

What is the innervation of the muscles in the 4th layer of plantar aspect of the foot?

Answer 18

Both sets of interossei are innervated by lateral plantar nerve

Question 19

What presentation is characteristic of torn extensor digitorum brevis muscle fibres?

Answer 19

Results in a heamatoma producing a swelling anteromedial to the lateral malleolus. (often confused for a sprained ankle)

Question 20

What will happen if the medial plantar nerve is compressed?

Answer 20

Can be compressed by abductor hallucis muscle

Causes aching, numbness and paraethesia on medial sole of foot