Anatomy of the foot

How many bones are in the foot?

26

How are the arches in the foot maintained?

Bony geometry, ligaments, and active muscle support

What is the retinacula?

Pulley system organizing tendons

What are the plantar compartments?

Medial

Central

Lateral

Interosseous

What is the primary action of the dorsal compartment?

Toe extension

What is the innervation of the dorsal compartment?

Deep fibular

What is the primary action of the plantar medial compartment?

Hallux support

Medial arch

What is the innervation of the plantar medial compartment?

Medial plantar nerve

What is the primary action of the plantar central compartment?

Toe flexion

Arch support

What is the innervation of the plantar central compartment?

Medial and lateral plantar nerves

What is the primary action of the plantar lateral compartment?

5th toe support

Lateral stability

What is the innervation of the plantar lateral compartment?

Lateral plantar nerve

What is the primary action of the interosseous compartment?

Toe abduction

Toe adduction

What is the innervation of the interosseous compartment?

Lateral plantar nerve

Where do extrinsic muscles originate?

In the leg

What are the gross movements of the extrinsic muscles?

Dorsiflexion

Plantarflexion

Inversion

Eversion

Where do the extrinsic tendons cross?

Cross the ankle via retinacula

What are the extrinsic materials innervated by?

Nerves of the leg

Where do intrinsic materials originate?

Within the foot

What are the functions of the intrinsic materials?

Fine motor control

Toe stabilization

Arch support

Load distribution

Is there a retinacular passage for intrinsic materials?

No

What are intrinsic materials innervated by?

Terminal branches in foot

Medial plantar

Lateral plantar

Deep fibular

What are the functions of the dorsal intrinsic?

Assist toe extension

Largely redundant with EDL

Clinically meaningful in neuropathy and nerve injury assessment

What is the primary innervation of the dorsal intrinsic?

Deep fibular nerve

What are the muscles in the dorsal intrinsic?

Extensor digitorum brevis (EDB)

Extensor hallucis brevis (EHB)

What is the origin of the extensor digitorum brevis?

Superolateral surface of the calcaneus

What is the insertion of the extensor digitorum brevis?

Lateral sides of tendons of extensor digitorum longus of toes 2 to 4

What is the action of extensor digitorum brevis?

Extension of toes 2 to 4

What is the innervation of extensor digitorum brevis?

Deep fibular nerve (S1, S2)

What is the origin of the extensor hallucis brevis?

Superolateral surface of the calcaneus

What is the insertion of the extensor hallucis brevis?

Base of proximal phalanx of great toe

What is the action of extensor hallucis brevis?

Extension of MTP joint of great toe

What is the innervation of extensor hallucis brevis?

Deep fibular nerve (S1, S2)

What layer is abductor hallucis in?

1

What compartment is abductor hallucis in?

Medial

What layer is flexor digitorum brevis in?

1

What compartment is flexor digitorum brevis in?

Central

What layer is abductor digit minimi in?

1

What compartment is abductor digiti minimi in?

Lateral

What layer is quadratus plantae in?

2

What compartment is quadratus plantae in?

Central

What layer is lumbricals in?

2

What compartment are the lumbricals in?

Central

What layer is the flexor hallucis brevis in?

3

What compartment is the flexor hallucis brevis in?

Medial

What layer is the adductor hallucis in?

3

What compartment is the adductor hallucis in?

Central

What layer is the flexor digiti minimi in?

3

What compartment is the flexor digiti minimi in?

Lateral

What layer is the dorsal interossei in?

4

What compartment is the dorsal interossei in?

Interosseous

What layer is plantar interossei in?

4

What compartment is plantar interossei in?

Interosseous

What is the most superficial layer in the foot?

Plantar layer 1

Does plantar layer 1 span all 3 compartments?

Yes

Why is plantar layer 1 known as the first responder layer?

Most directly palpable

Most visibly affected by atrophy

Most commonly lost first in peripheral neuropathy

What is the origin of the abductor hallucis?

Medial process of calcaneal tuberosity

What is the insertion of the abductor hallucis?

Medial side of base of proximal phalanx of great toe

What is the action abductor hallucis?

Abducts and flexes great toe at MTP joint

What is the innervation of the abductor hallucis?

Medial plantar nerve (S1-S3)

What is the origin of the flexor digitorum brevis?

Medial process of calcaneal tuberosity and plantar aponeurosis

What is the insertion of the flexor digitorum brevis?

Sides of plantar surface of middle phalanges of digits 2-5

What is the action of the flexor digitorum brevis?

Flexes digits 2-5 at PIP joints

What is the innervation of the flexor digitorum brevis?

Medial plantar nerve (S1-S3)

What is the origin of the abductor digit mini?

Lateral and medial processes of calcaneal tuberosity, and plantar aponeurosis

What is the insertion of the abductor digiti minimi?

Lateral side of base of proximal phalanx of 5th digit

What is the action of the abductor digiti minimi?

Abducts 5th digit at MTP joint

What is the innervation of the abductor digit minimi?

Lateral plantar nerve (S1-S3)

What compartment are the plantar level 2 muscles in?

Central compartment

What do the plantar level 2 muscles have a role in?

Modifying and redirecting the pull of extrinsic long flexor tendons

What is the origin of the quadratus plantae?

Medial surface of calcaneus and lateral process of calcaneal tuberosity

What is the insertion of the quadratus plantae?

Lateral side of tendon of FDL in proximal sole of foot

What is the action of the quadratus plantae?

Assists in flexor digitorum tendon in flexing toes 2-5

What is the innervation of the quadratus plantae?

Lateral plantar nerve (S1-S3)

What is the origin of the 1st lumbrical?

Medial side of tendon of FDL associated with toe 2

What is the origin of the 2nd-4th lumbricals?

Adjacent surfaces of adjacent tendons of FDL

What is the insertion of the lumbricals?

Medial free margins of extensor hoods of toes 2-5

What is the action of the lumbircals?

Flexion of MTP joint and extension of IP joints

What is the innervation of the 1st lumbrical?

Medial planter nerve (S2, S3)

What is the innervation of the 2nd-4th lumbricals?

Lateral planter nerve (S2-S3)

Does plantar layers 3 Spain all three compartments?

Yes

Where is the plantar surface 3?

Deep to long flexor tendons and lumbricals

What is the origin of the flexor hallucis brevis?

Plantar surface of cuboid and lateral cuneiform

Tendon of tibialis posterior

What is the insertion of the flexor hallucis brevis?

Lateral and medial sides of bases of proximal phalanx of great toe

What is the action of the flexor hallucis brevis?

Flexes MTP joint of great toe

What is the innervation of the flexor hallucis brevis?

Medial plantar nerve (S1-S2)

What is the origin of the adductor hiatus's transverse head?

Transverse metatarsal ligaments and MTP capsules of toes 3-5

What is the origin of the adductor hallucis's oblique head?

Bases of metatarsals 2-4

Sheath of fibularis longus

What is the insertion of the adductor hallucis?

Lateral side of base of proximal phalanx of great toe

What is the action of the adductor hallucis?

Adducts great toe at MTP joint

What is the innervation of the adductor hallucis?

Lateral plantar nerve (S2-S3)

What is the origin of the flexor digiti minimi?

Base of the 5th metatarsal

Sheath of fibularis longus

What is the insertion of the flexor digiti minimi?

Lateral side of base of proximal phalanx of 5th digit

What is the action of the flexor digiti minimi?

Flexes 5th digit at MTP joint

What is the innervation of the flexor digiti minimi?

Lateral plantar nerve (S2-S3)

What is the deepest layer?

Plantar layer 4

What is plantar layer 4 directly adjacent to?

Metatarsal shafts

What is the origin of the dorsal interossei?

Sides of adjacent metatarsals

What is the insertion of the dorsal interossei?

Extensor hoods and bases of proximal phalanges of digits 2-4

What is the action of the dorsal interossei?

Abduction of digits 2-4 at MTP joints

MTP flexion