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Extensor hallucis longus tendon

The extensor hallucis longus (EHL) tendon is the distal extension of the extensor hallucis longus muscle. It is a long, thin tendon that crosses the anterior ankle joint and continues over the dorsum of the foot to insert into the distal phalanx of the great toe.

The tendon becomes visible and palpable on the dorsum of the foot when the great toe is actively extended. It plays a vital role in hallux extension and assists in ankle dorsiflexion. Because of its superficial location and long course, the EHL tendon is vulnerable to trauma, laceration, entrapment, and tendinopathy.

Origin, Course, and Insertion

  • Origin: Continuation of the tendon formed by the extensor hallucis longus muscle in the anterior compartment of the leg

  • Course: Passes deep to the superior and inferior extensor retinacula at the ankle, running across the dorsum of the foot toward the great toe

  • Insertion: Dorsal surface of the base of the distal phalanx of the hallux

  • Accessory slips: In some individuals, may send fibers to the proximal phalanx or capsule of the first metatarsophalangeal joint

Relations

  • Superiorly: Crosses anterior to the ankle joint deep to the extensor retinacula

  • Inferiorly: Lies superficial to the dorsal bones and joints of the hallux

  • Medially: Close to the tibialis anterior tendon

  • Laterally: Related to the extensor digitorum longus tendons

  • Posteriorly: Associated with the anterior tibial vessels and deep fibular nerve

Function

  • Extension of the great toe: Main tendon responsible for extending the hallux at both MTP and IP joints

  • Assists in dorsiflexion: Works with tibialis anterior to dorsiflex the ankle

  • Stabilization: Helps maintain balance during walking and running by stabilizing the medial side of the foot

  • Clinical marker: Prominence of the tendon on forced hallux extension is a useful surface landmark

Clinical Significance

  • Tendon injuries: Lacerations, ruptures, and partial tears may occur from trauma or overuse

  • Tendinopathy: Overuse in athletes, dancers, or climbers may lead to pain and thickening

  • Entrapment: Can be compressed beneath the extensor retinaculum causing anterior ankle pain

  • Surgical importance: Tendon transfers (EHL → EDL) may be performed in cases of foot drop

  • Imaging role: MRI is best for tendon evaluation; CT is useful for chronic calcification or trauma

MRI Appearance

  • T1-weighted images:

    • Tendon: low signal (dark band) with smooth, continuous margins

    • Muscle belly (if included): intermediate signal intensity

    • Surrounding fat: bright, enhancing delineation of tendon course

    • Partial tear: focal discontinuity with intermediate-to-bright signal at defect site

  • T2-weighted images:

    • Normal tendon: very low signal (dark, homogeneous linear structure)

    • Normal muscle (proximal): intermediate but slightly darker than T1

    • Tendinopathy: focal or diffuse bright hyperintensity within tendon substance

    • Fluid or tenosynovitis: bright signal outlining tendon sheath

  • STIR:

    • Normal tendon: dark to intermediate

    • Pathology: hyperintense signal along tendon sheath or insertion, indicating edema, inflammation, or partial tear

    • Normal muscle: intermediate-to-dark

  • Proton Density Fat-Saturated (PD FS):

    • Normal tendon: dark homogeneous band

    • Partial tears or tendinitis: bright linear or spot-like hyperintense areas within or around tendon

    • Muscle: intermediate-to-dark under normal conditions

    • Excellent for detecting microtears, peritendinitis, and subtle sheath effusions

  • T1 Fat-Sat Post-Contrast:

    • Normal tendon: minimal or no enhancement

    • Inflamed tendon sheath: shows rim or diffuse enhancement

    • Tendinitis or tenosynovitis: marked enhancement of surrounding soft tissue

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

CT Appearance

Non-Contrast CT:

  • Tendon: slender soft-tissue density anterior to ankle joint and dorsum of foot

  • Surrounding fat planes clearly visible

  • Chronic tendinopathy may show calcification or ossification near tendon insertion

  • Subtle displacement may indicate partial rupture

Post-Contrast CT (standard):

  • Tendon: enhances minimally

  • Inflamed tendon sheath: shows thin rim enhancement

  • Useful for detecting post-surgical changes, calcific deposits, or chronic inflammatory thickening

MRI image

Extensor hallucis longus tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Extensor hallucis longus tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI image

Extensor hallucis longus tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

CT image

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CT image

Extensor hallucis longus tendon ct axial 1

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Extensor hallucis longus tendon ct axial 2

MRI image

Extensor hallucis longus tendon of the Foot axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00000

MRI image

Extensor hallucis longus tendon of the Foot axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_0002

MRI image

Extensor hallucis longus tendon of the Foot axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00003

MRI image

Extensor hallucis longus tendon of the Foot axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00001

MRI image

Extensor hallucis longus tendon of the Foot sag cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

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CT image

Extensor hallucis longus tendon ct axial