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Central plantar muscles of the foot
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The plantar muscles of the foot are traditionally studied in either layers or groups. If studying by layers, we can organise these muscles into four primary layers:
- 1st layer: abductor 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: plantar and dorsal interossei
The plantar muscles of the foot can alternatively be considered by medial, central and lateral groups. This article will discuss the central plantar muscles.
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Flexor digitorum brevis |
Origins: Medial process of calcaneal tuberosity, Plantar aponeurosis Insertions: Middle phalanges of digits 2-5 Innervation: Medial plantar nerve (S1-S3) Functions: Metatarsophalangeal joints 2-5: Toe flexion; Supports longitudinal arch of foot |
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Quadratus plantae |
Origins: Medial process of calcaneus bone, Lateral process of calcaneal tuberosity Insertions: Tendon of flexor digitorum longus Innervation: Lateral plantar nerve (S1-S3) Functions: Metatarsophalangeal joints 2-5: Toe flexion |
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Lumbricals (4) |
Origins: Tendons of flexor digitorum longus Insertions: Medial bases of proximal phalanges and extensor expansion of digits 2-5 Innervation: Lumbrical 1: Medial plantar nerve (S2,S3); Lumbricals 2-4: Lateral plantar nerve (S2-S3) Functions: Metatarsophalangeal joints 2-5: Toe flexion, Toes adduction; Interphalangeal joints 2-5: Toes extension |
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Plantar interossei (3) |
Origins: Medial aspects of metatarsal bones 3-5 Insertions: Medial bases of proximal phalanges and extensor expansion of digits 3-5 Innervation: Lateral plantar nerve ( S2-S3) Functions: Metatarsophalangeal joints 3-5: Toe flexion, Toes adduction; Interphalangeal joints 3-5: Toes extension |
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Dorsal interossei (4) |
Origins: Opposing sides of metatarsal bones 1-5 Insertions: 1: Medial base of proximal phalanx of digit 2 2-4: Lateral bases of proximal phalanges and extensor expansion of digits 2-4 Innervation: Lateral plantar nerve ( S2-S3) Functions: Metatarsophalangeal joints 2-4: Toe flexion, Toe abduction; Interphalangeal joints 2-4: Toe extension |
| Mnemonic |
Muscles innervated by the
medial plantar nerve can be remembered as LAFF muscles (stands for: first Lumbrical, Abductor hallucis, Flexor digitorum brevis, Flexor hallucis brevis) |
This article will discuss the central plantar muscles.
Anatomy and supply
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The central muscles of the foot sole lie within the central compartment between the muscles of the big and little toe.
The compartment comprises numerous short foot muscles in different layers. Together they form the central surface of the foot sole. Adductor hallucis is a special case because it is anatomically located in the central compartment of foot, but the muscle is functionally grouped with the medial plantar muscles of foot because it acts on the great toe (hallux).
Both the medial and lateral nerves (branches of the tibial nerve (L5-S2)) are responsible for the innervation of the central plantar muscles.
Flexor digitorum brevis muscle
The FBD originates at the medial process of the calcaneal tuberosity and plantar aponeurosis. Distally it divides into four tendons moving towards the second to fifth toes. At the proximal phalanges these tendons separate further into two smaller tendons, which finally insert along the medial and lateral aspects of the middle phalanges.
(Innervation: medial plantar nerve)
Quadratus plantae muscle
This muscle runs from the medial surface of the calcaneus, and lateral process of the calcaneal tuberosity to the tendon of the flexor digitorum longus muscle.
(Innervation: lateral plantar nerve)
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Lumbrical muscles (I-IV)
The group of muscles originate at the tendons of the flexor digitorum longus muscle and insert medially into the bases of the second through fifth proximal phalanges as well as the dorsal aponeurosis/extensor expansions of the same digits.
(Innervation: medial plantar nerve (I), lateral plantar nerve (II-IV))
Plantar interossei muscles I-III
The plantar interossei extend from the medial aspects of the third through fifth metatarsal bones to the medial side and extensor expansions of the proximal phalanx of the same toes
(Innervation: lateral plantar nerve)
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Dorsal interossei muscles I-IV
The four dorsal interossei are two-headed, or bipennate muscles, found interposed between the five metatarsal bones of the foot.
The first lumbrical inserts into the medial aspect of the base of the second proximal phalanx. The second through fourth lumbricals however, have their insertions along the lateral aspects of the bases of the proximal phalanges of the second through fourth toes, in addition to the extensor expansions of the same toes.
(Innervation: lateral plantar nerve)
Anatomical relations
The flexor digitorum brevis muscle lies superficially under the plantar aponeurosis and marks the largest muscle in the central compartment. The quadratus plantae muscle runs immediately deep to it. The origins of the lumbrical muscles are located at the distal end of the quadratus plantae muscle.
In comparison the plantar and dorsal interossea muscles lie deeper within the plantar aspect of the foot.
In addition to the above mentioned muscles, the central compartment of the foot sole comprises the oblique head of the adductor hallucis muscle, the posterior tibial artery and vein and the tibial nerve.
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However the vessels and nerves divide quite early into a medial and lateral bundle entering the medial and lateral compartment of the foot sole. Distally the branches meet again in the central compartment forming an arterial and venous arcade (plantar arch and plantar venous arch).
Function
The muscles of the central compartment fulfill various tasks.
- The flexor digitorum brevis muscle is involved in flexion of the second to fifth toes and actively supports the longitudinal arch of the foot.
- The quadratus plantae muscle does not move any joints but has a rather special function: By pulling at the tendon of the flexor digitorum longus muscle it shifts the tendon’s force effect to the longitudinal direction increasing the effectiveness of the toe flexion of the muscle.
- The lumbricals, as well as the plantar interossei muscles flex and adduct the toes at the metatarsophalangeal joints (closing the spread toes). They also extend the toes at the interphalangeal joints.
- The dorsal interossei muscles flex the toes as well but in contrast cause abduction at the metatarsophalangeal joints (spreading of the toes). They also extend the toes at the interphalangeal
Test your knowledge on the muscles of the foot with this quiz.
Clinical note
The plantar aponeurosis passively contributes to the longitudinal arch of the foot. If it is chronically strained (e.g. in athletes and elderly people) a plantar fasciitis may develop.
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This is a degenerative change of the plantar aponeurosis at the origin at the calcaneus. Typically the X-ray shows a dense ossification (calcaneal or heel spur).
Being overweight, having metabolic and rheumatic diseases are the most important risk factors. The affected people experience a slow and subtle, stress-dependent pain at the heel and the sole of the foot.
In addition to orthopedic insoles, physiotherapy and pain medication (if required) good results are achieved with shock wave therapy.
Central plantar muscles of the foot: want to learn more about it?
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