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Adductor hallucis muscle

The adductor hallucis muscle is a deep intrinsic muscle of the sole of the foot that plays a crucial role in adducting the great toe and stabilizing the transverse and longitudinal arches. It lies in the third layer of plantar muscles, deep to the tendons of the flexor digitorum longus and flexor hallucis longus, and lateral to the flexor hallucis brevis.

The muscle has two distinct heads — oblique and transverse — which converge to form a common tendon that inserts on the lateral aspect of the base of the proximal phalanx of the hallux. Together, they provide dynamic stability to the first metatarsophalangeal (MTP) joint and assist in maintaining foot balance during gait and toe-off.

Synonyms

  • Adductor of the great toe

  • Hallucis adductor muscle

Origin, Course, and Insertion

  • Oblique head origin: From the bases of the second, third, and fourth metatarsals and the sheath of the fibularis longus tendon

  • Transverse head origin: From the plantar ligaments of the third, fourth, and fifth MTP joints and the deep transverse metatarsal ligament

  • Course: The fibers of both heads pass obliquely and medially toward the great toe; the oblique head lies deep to the flexor hallucis brevis

  • Insertion: The two heads unite in a common tendon that inserts into the lateral side of the base of the proximal phalanx of the hallux and into the lateral sesamoid bone

Tendon Attachments

  • The common tendon blends with the lateral tendon of the flexor hallucis brevis

  • A small sesamoid bone is often embedded in its insertional tendon

  • Assists the lateral head of flexor hallucis brevis in stabilizing the first MTP joint

Relations

  • Superiorly: Deep plantar metatarsal vessels and interossei muscles

  • Inferiorly: Plantar aponeurosis

  • Medially: Flexor hallucis brevis and the great toe

  • Laterally: Flexor digiti minimi brevis

  • Posteriorly: Deep branch of the lateral plantar nerve and artery

Nerve Supply

  • Deep branch of the lateral plantar nerve (S2–S3), branch of the tibial nerve

Arterial Supply

  • Plantar arterial arch (from lateral plantar artery)

  • Additional contributions from deep plantar artery

Venous Drainage

  • Plantar venous arch and deep plantar veins, draining into the posterior tibial vein

Function

  • Adduction of great toe: Pulls the hallux medially toward the second toe

  • Arch stabilization: Supports transverse and medial longitudinal arches

  • Dynamic balance: Aids in propulsion and stabilization during gait

  • Synergistic action: Works with the flexor hallucis brevis and interossei muscles for fine control of toe movement

Clinical Significance

  • Overuse injuries: Repetitive strain may cause plantar pain or medial forefoot discomfort

  • Hallux valgus: Chronic imbalance or tightness of adductor hallucis contributes to lateral deviation of the great toe

  • Nerve compression: Deep branch of lateral plantar nerve entrapment can weaken the muscle

  • Tendon pathology: May present with localized tenderness along the first MTP joint

  • Surgical relevance: Important in bunion correction and first ray stabilization procedures

MRI Appearance

  • T1-weighted images:

    • Normal muscle: intermediate signal intensity with well-defined fascicular structure

    • Tendon: low signal (dark) inserting on the lateral side of proximal phalanx

    • Sesamoid (if present): low-signal cortex with intermediate marrow

    • Surrounding fat: bright, outlining muscle borders clearly

  • T2-weighted images:

    • Normal muscle: intermediate-to-low signal intensity, slightly darker than on T1

    • Tendon: uniform low signal

    • Pathology: bright hyperintense signal in cases of strain, inflammation, or partial tear

    • Peritendinous or plantar edema: high T2 signal in overuse or compression injuries

  • STIR:

    • Normal muscle: intermediate-to-dark signal

    • Pathologic changes (edema, inflammation, strain): appear as bright hyperintense regions

    • Useful for identifying early myotendinous or fascial edema

  • Proton Density Fat-Saturated (PD FS):

    • Normal muscle: intermediate-to-dark, homogeneous appearance

    • Pathology: focal or diffuse bright hyperintensity within muscle fibers or tendon insertion

    • Sensitive to mild strain, tendinopathy, and peritendinous inflammation

  • T1 Fat-Sat Post-Contrast:

    • Normal muscle: uniform mild enhancement

    • Tendinitis or muscle inflammation: focal enhancement

    • Chronic tendinopathy or scar: peripheral rim enhancement with central low-signal fibrosis

CT Appearance

Non-Contrast CT:

  • Muscle: homogeneous soft-tissue density deep to plantar fascia

  • Tendon: fine soft-tissue band inserting laterally on the proximal phalanx

  • Sesamoid bone (if present): dense oval ossicle lateral to the first metatarsal head

  • Chronic overuse or irritation: may show sclerosis or cortical irregularity around insertion

Post-Contrast CT (standard):

  • Muscle enhances homogeneously

  • Inflamed tendon or myotendinous junction: shows focal enhancement

  • Useful for detecting calcifications, ossifications, or chronic scar tissue near the first MTP joint

MRI images

Adductor hallucis muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Adductor hallucis muscle axialcross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI images

Adductor hallucis muscle coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Adductor hallucis muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI image

Adductor hallucis muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

CT image

Adductor hallucis muscle ct axial image