Foot Muscles – Anatomy, Nerve Supply, Functions

Foot Muscles acting on the foot can be divided into two distinct groups; extrinsic and intrinsic muscles. The extrinsic muscles arise from the anterior, posterior and lateral compartments of the leg. They are mainly responsible for actions such as eversion, inversion, plantarflexion and dorsiflexion of the foot.

The foot is a complex mechanical structure of the human body composed of 33 joints, 26 bones, and more than a hundred muscles, tendons, and ligaments that all work together to bear weight, allow for locomotion, and transmit force. The joints of the foot are made wherever two or more of the foot bones meet

There are 29 muscles associated with the human foot. (10 foot/ankle and 19 intrinsic) Ten of these muscles originate outside of the foot itself but cross the ankle joint to act on the ankle joint and help position the foot.  The other 19 muscles are referred to as intrinsic muscles of the foot and act only within the foot. The muscles covered in this article serve various roles in gait as well as posture. These muscles are also aided by the plantar fascia, managing the mechanical vectors of the foot. The muscles of the foot influence the posture and the shape of the foot, as well as providing the ability to transmit muscle tension not only towards the ground but also towards the whole body system.

Blood Supply of Foot Muscles

The blood supply to the foot begins primarily with the popliteal artery. The popliteal artery branches off the large superficial femoral artery and gives rise to the three main branches supplying the lower leg and foot. The three branches from proximal to distal are the anterior tibial artery, peroneal artery, and posterior tibial artery.  The anterior tibial artery continues distally to supply the anterior and dorsal portions of the foot.  Once the anterior tibial artery passes under the extensor retinaculum, it becomes the dorsalis pedis.  This artery is commonly palpated for a pedal pulse. The dorsalis pedis continues under the extensor hallucis longus and passes between it and the extensor digitorum longus.  The dorsalis pedis has three lateral branches named the proximal and distal tarsal arteries and the arcuate artery, and two medial branches named the medial tarsal arteries. The arcuate artery branches at the level of the 1st tarsal-metatarsal joint and courses over the metatarsals 2 to 4 to give rise to the dorsal metatarsal arteries 2 to 4. The first dorsal metatarsal artery branches directly off the dorsalis pedis. The metatarsal branches supply the dorsal interosseous muscles of the foot. The peroneal artery supplies the muscles of the lateral leg and the posterior foot.  Finally, the posterior tibial artery supplies the posterior and lateral leg as well as the plantar surface of the foot.[rx]

The venous system of the lower limbs is composed of deep veins (which run between the muscles) and superficial veins (which constitute a complex network just below the skin). The two systems are joined by transfascial valved communications that constitute a real system, that of the perforating veins. The perforating veins have the function of favouring the outflow of the blood that flows in the system superficial (about 10%) towards the deep system.

In the sole of the foot, there is a sort of sponge, consisting of a complicated intertwining of superficial and deep veins which, at each step, is emptied by compression on the ground. Thanks to this mechanism, the blood is pushed over the ankle up to the calf.

The venous system originates in the microcirculation from the arterial capillaries (afferent branch) to continue with the venous capillaries that converge in the collecting venules first and then in the collecting veins, thus constituting the initial efferent branch of venous macrocirculation.

In the anterior region the dorsal venous network of the foot through the intercapitular veins that pass through the interdigital spaces; the digital veins, joining two to two in the interdigital spaces, originate the metatarsal veins that are directed in the deep plantar venous arch, converging in the lateral plantar veins; these, after joining posteriorly with the medial plantar veins, originate the two posterior tibial veins. The anterior tibialis originate from the deep veins of the dorsal region of the foot. The medial marginal vein of the foot ascending anterior to the medial malleolus forms the internal saphenous vein or the great saphenous vein. The lateral marginal vein of the foot ascending anterior to the lateral malleolus forms the small saphenous vein.

The lymph drained from the lower limb reaches the external and common iliac lymph node chains. The fingers and the sole of the foot are rich in superficial lymphatic vessels, which gather in the medial and lateral collectors. The lymph drained deeply from the foot, concerns above all the articular area, bone and muscle and aponeurosis; the lymph gathers in the popliteal and femoral collectors.

Nerves Supply of Foot Muscles

There will be discussion regarding innervation of the various muscles in greater detail in the sections that follow.  The initial nerve that gives rise to most of the innervation of the lower extremity is the sciatic nerve.  The sciatic nerve makes its way out of the lumbosacral plexus and passes under the piriformis muscle before traveling distally.  Around the distal third of the femur, the sciatic nerve branches to give rise to the common fibular nerve and the tibial nerve.  The tibial nerve continues distally to give rise to the medial calcaneal branches, the medial sural cutaneous nerve, and the medial and lateral plantar nerves.  The common peroneal nerve gives rise to two main branches, the superficial peroneal and the deep peroneal nerves. The superficial peroneal nerve primarily gives rise to cutaneous branches that receive sensory information from the skin.  The deep peroneal nerve supplies motor function to many of the muscles responsible for dorsiflexion of the foot.[rx][rx]

The nerves of the foot, their branches, and their origins include [rx]

• Superficial peroneal (fibular) nerve (arises from the common fibular nerve)
• Deep peroneal (fibular) nerve (arising from the common fibular nerve)
• Tibial nerve (arises in the popliteal fossa as a division of the sciatic nerve)
  • Medial plantar nerve (arises from the larger terminal branch of the tibial nerve)
    • Digital nerves (arise from both the medial and lateral plantar nerves)
  • Lateral plantar nerve (arises from the smaller terminal branch of the tibial nerve)
    • Inferior calcaneal nerve, also known as Baxter’s nerve (typically arises as the first branch of the lateral plantar nerve)
  • Medial calcaneal nerve (typically arises from the tibial nerve)
• Sural nerve (typically arises from branches of both the common fibular and tibial nerves)
• Saphenous nerve (arises from the femoral nerve)

The sural nerve originates from branches of both the common fibular nerve and the tibial nerve. It supplies the lateral hind and midfoot. The calcaneal branches originate from the tibial and sural nerves and sensory innervation to the skin of the heel.[rx][rx]

Sciatic

• Tibial

  • Medial sural cutaneous
  • Medial calcaneal

  • Medial plantar

    • Common plantar digital nerves
    • Proper plantar digital nerves

  • Lateral plantar

    • Deep branch

    • Superficial branch

      • Common plantar digital nerves
      • Proper plantar digital nerves

• Common fibular (peroneal)

  • Deep fibular

    • Lateral terminal branch
    • Medial terminal branch

  • Superficial

    • Medial dorsal cutaneous
    • Intermediate dorsal cutaneous

• Sural

  • Lateral dorsal cutaneous
  • Lateral calcaneal

Muscles Attachment of Foot Muscles

The fascia plays a key role in dividing and attaching muscles in the foot. The relationship of the fascia with the muscles can be further described by the compartment they are in.

• Medial compartment: The medial plantar fascia overlies the abductor hallucis, flexor hallucis brevis, and the flexor hallucis longus tendon.
• Central compartment: The central plantar fascia overlies the flexor digitorum brevis, the tendon of the flexor hallucis longus, the tendons and musculature of the flexor digitorum longus, the quadratus plantae, the lumbricals, and the adductor hallucis.
• Lateral compartment: The lateral plantar fascia overlies the abductor and flexor digiti minimi brevis.
• Interosseous compartment: The plantar and dorsal interosseous fascias border the interosseous muscles.
• Dorsal compartment: The dorsal fascia overlies the extensors hallucis brevis and extensor digitorum brevis.

To simplify the organization of the muscles, the following will break them up into those that act upon the foot and ankle and those classified as intrinsic.[rx][rx][rx]

Foot and Ankle

Peroneus Longus

• The peroneus longus is one of the three muscles that span the lateral leg – peroneus may also be interchanged with fibular, referring to the lateral bone of the lower leg running deep to the peroneal muscles
• Origin: The peroneus longus muscle originates on the head of the fibula and the upper half of the fibular shaft – this muscle crosses the ankle joint and courses deep into the foot and passes into a groove of the cuboid bone.
• Insertion: the posterolateral aspect of the medial cuneiform bone and the lateral portion of the base of the first metatarsal
• Action: The peroneus longus acts to evert the foot, plantarflex the ankle and adds support to the transverse arch of the foot
• Blood Supply: Anterior tibial artery
• Innervation: Superficial peroneal nerve

Peroneus Brevis

• The peroneus brevis is another of the three muscles spanning the lateral leg and may also be called fibularis brevis, referring to the fibula
• Origin: The peroneus brevis originates on the inferior two-thirds of the lateral fibula and courses posteriorly to the lateral malleolus of the fibula ultimately
• Insertion: The styloid process of the fifth metatarsal
• Action: The primary action of the peroneus brevis is to evert the foot and plantar flex the ankle
• Blood Supply: Peroneal artery
• Innervation: The superficial peroneal nerve innervates the peroneus brevis muscle

Peroneus Tertius

• The peroneus tertius is the third and final muscle of the lateral peroneus or fibular muscles
• Origin: The peroneus tertius originates from the middle fibular shaft
• Insertion: The dorsal surface of the fifth metatarsal
• Action: Dorsiflex, evert, and abduct the foot
• Blood Supply: The peroneus tertius primarily receives its blood supply from the anterior tibial artery
• Innervation: Peroneus tertius innervation comes from the deep peroneal nerve, an innervation different than its similarly named peroneal counterparts

Anterior Tibialis

• The anterior tibialis is the most prominent muscle in the anterior leg and is often visible during dorsiflexion of the foot
• Origin: The lateral condyle of the tibia and the proximal half to two-thirds of the tibial shaft.
• Insertion: Occurs after passing under the extensor retinaculum and is on the medial and plantar surfaces of the medial cuneiform and base of the 1st metatarsal.
• Action: Dorsiflex the ankle and invert the hindfoot
• Blood Supply: Anterior tibial artery
• Innervation: Comes from the deep peroneal nerve

Posterior Tibialis

• Origin: The superior two-thirds of the medial posterior surface of the tibia
• Insertion: The tendon courses distally, splitting into two at the calcaneonavicular ligament, to insert on the tuberosity of the navicular bone (superficial slip) and the plantar surfaces of the metatarsals two to four (deep slip)
• Action: The posterior tibialis is the primary inverter of the foot but also adducts, plantar flexes, and aides in supination of the foot
• Blood Supply: Sural, peroneal, and posterior tibial arteries
• Innervation: Tibial nerve

Extensor Digitorum Longus

• Origin: Lateral tibial condyle and continues distally to split into four tendons after the level of the extensor retinaculum
• Insertion: Dorsum of the middle and distal phalanges
• Action: Extend the second through fifth digits and dorsiflex the ankle
• Blood Supply: anterior tibial artery
• Innervation: deep peroneal nerve

Flexor Digitorum Longus

• Origin: Posterior surface of the tibia distal to the popliteal line
• Insertion: Continues distally to split into four individual tendons which insert on the plantar surfaces of the bases of the second through fifth distal phalanges
• Action: Flex the digits two through five and may aid in plantar flexion of the ankle
• Blood Supply: Posterior tibial artery
• Innervation: Tibial nerve

Flexor Hallucis Longus

• Origin: inferior two-thirds of the posterior fibula
• Insertion: The plantar surface of the base of the distal phalanx of the great toe
• Action: Flex the great toe but may minimally supinate and plantar flex the ankle
• Blood Supply: Peroneal and posterior tibial artery
• Innervation: Tibial nerve

Gastrocnemius

• The gastrocnemius is the most superficial calf muscle
• Origin: femoral condyles
• Insertion: thick Achilles tendon inserting on the calcaneus.
• Action: Plantarflex the ankle.
• Blood Supply: Sural branch of the popliteal artery
• Innervation: Tibial nerve

Soleus

• The soleus is the deep muscle of the posterior leg and makes up most of the bulk of the calf
• Origin: Upper quarter of the posterior fibula and the middle third of the posterior tibial shaft
• Insertion: The soleus eventually joins the gastrocnemius to for the Achilles tendon to insert on the calcaneus
• Action: The action is to plantarflex the ankle
• Blood Supply: Posterior tibial, peroneal, and sural arteries
• Innervation: Tibial nerve

Intrinsic

Dorsal

Extensor Digitorum Brevis

• Origin: Dorsal surface of the calcaneus
• Insertion: The base of the proximal phalanx of digits two through four
• Action: Extend the toes
• Blood Supply: Dorsalis pedis
• Innervation: Deep peroneal nerve

Dorsal Interosseus

• The dorsal interossei muscles (3) exist between digits two through five – the two adjacent muscles form a central tendon and act to abduct the metatarsal-phalangeal joints and innervation comes from the lateral plantar nerve

Extensor Hallucis Brevis

• Origin: Dorsal surface of the calcaneus
• Insertion: The base of the proximal phalanx of the great toe
• Action: Extend the great toe
• Blood Supply: Dorsalis pedis.
• Innervation: Deep peroneal nerve

Plantar

1st layer

Abductor Hallucis

• Origin: Calcaneal tuberosity
• Insertion: Base of the great toe and the proximal phalanx.
• Action: Abduct the great toe
• Blood Supply: Medial plantar artery
• Innervation: Medial plantar nerve

Flexor Digitorum Brevis

• Origin: Calcaneal tuberosity
• Insertion: The middle phalanx of digits two thorugh five
• Action: Flex the digits two through five
• Blood Supply: Medial plantar artery
• Innervation: Medial plantar nerve

Abductor Digiti Minimi

• Origin: Calcaneal tuberosity
• Insertion: Base of the fifth metatarsal
• Action: Abduct the 5th digit
• Blood Supply: Lateral plantar artery
• Innervation: Lateral plantar nerve lateral plantar artery

2nd Layer

Quadratus Plantae

• Origin: Plantar surface of the calcaneus
• Insertion: Flexor digitorum longus tendon
• Action: Help flex the distal phalanges
• Blood Supply: Lateral plantar artery
• Innervation: Llateral plantar nerve

Lumbricals

• There are four muscles referred to as lumbricals in the foot
• Origin: Flexor digitorum longus tendon
• Insertion: Extensor digitorum longus tendon
• Action: Flex the metatarsophalangeal joints and extend the interphalangeal joints
• Blood Supply: Medial and lateral plantar arteries
• Innervation: Medial and lateral plantar nerve

3rd layer

Flexor Hallucis Brevis

• Origin: The cuboid and the lateral cuneiform
• Insertion: Proximal phalanx of the great toe
• Action: Flex the great toe
• Blood Supply: Medial plantar artery
• Innervation: Medial plantar nerve

Oblique and Transverse Head of Adductor Hallucis

• The adductor hallucis has two heads, an oblique head, and a transverse head
• Origin: The oblique head originates at the proximal ends of the metatarsals two thourgh four, and the transverse head originates via MTP ligaments of digits three through five
• Insertion: inserts at the proximal phalanx of the great toe
• Action: The primary action is to adduct the great toe
• Blood Supply: First plantar metatarsal artery
• Innervation: Deep branch of lateral plantar

Flexor Digiti Minimi Brevis

• Origin: Base of the fifth metatarsal
• Insertion: Proximal phalanx of the fifth metatarsal
• Action: The primary action is to flex the fifth digit
• Blood Supply: Lateral Plantar artery
• Innervation: Lateral plantar nerve

4th layer

Plantar Interosseous

• The plantar interossei (3)
• Origin: medial aspect of the individual metatarsals of digits three through five
• Insertion: The proximal phalanges
• Action: Adduct the digits
• Blood Supply: Plantar metatarsal artery
• Innervation: Lateral plantar nerve

Functionally, the osseous structures of the foot form three arches. The calcaneus, cuboid, fourth and fifth rays form the rigid lateral arch. The medial arch can dynamically vary in shape, allowing for uneven terrain and has the medial three rays, cuneiforms, navicular, talus, and calcaneus.  Finally, the transverse arch runs obliquely along the tarsometatarsal joints.[rx]

Seven tarsal bones

• Cuboid bone
• Calcaneus or heel bone
• Three cuneiforms (medial, middle and lateral)
• Navicular bone
• The talus bone which is just below the ankle joint

Five metatarsal bones: number 1 to 5 medial to lateral

Fourteen Phalanges

• The first digit has two phalanges.
• The second through fifth digits each have three phalanges

Sesamoid bones

• The foot also has sesamoid bones that help improve stability and function. The two sesamoid bones are near the first metatarsal bone, where it connects to the big toe. Both sesamoids are within the tendon of flexor hallucis brevis. One sesamoid is usually located on the lateral aspect of the first metatarsal, whereas the other one is often on the medial side. In some individuals, only a single sesamoid may be present near the first metatarsal phalangeal joint.

Foot compartments

• The forefoot contains the phalanges and metatarsals.
• The midfoot consists of the five tarsal bones, three cuneiforms, the navicular, and the cuboid.
• The hindfoot is composed of two tarsal bones, the calcaneus and the talus.

Foot joints (major)

• Subtalar: articulation between the talus and calcaneus comprised of 6 facets, three on each bone, divided into two joints, anterior (anterior and middle facets) and posterior.[23]
• Chopart: Also known as the midtarsal joint. Joins the hindfoot to the midfoot. It is made up of the talonavicular and calcaneocuboid articulations. Named for the French surgeon Francois Chopart.[16]
• LisFranc: Junction of the mid and forefoot. It is comprised of the tarsometatarsal joints. Named for the French surgeon Jacques LisFranc de Saint-Martin.[20]
• Metatarsophalangeal: The articulations and associated connective tissues are commonly referred to as plantar plates. Injury to the first metatarsophalangeal joint is called turf toe.[22][24]

References