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Extensor digitorum brevis tendons

The extensor digitorum brevis (EDB) is a small muscle on the dorsum of the foot, situated deep to the tendons of the extensor digitorum longus. Its tendons provide extension to the 2nd, 3rd, and 4th toes, aiding in toe elevation during the swing phase of gait and in stabilizing the foot during propulsion.

The EDB is sometimes visible as a small prominence on the dorsolateral aspect of the foot, anterior to the lateral malleolus. It is an important structure in foot anatomy and clinical imaging, as its tendons may be mistaken for mass lesions or confused with accessory muscles such as the extensor digitorum accessorius.

Synonyms

  • Short extensor of the toes

  • Dorsal extensor of the lateral toes

Origin, Course, and Insertion

  • Origin: Anterolateral aspect of the calcaneus (superolateral surface), interosseous talocalcaneal ligament, and inferior extensor retinaculum

  • Course: The muscle passes obliquely forward and medially across the dorsum of the foot, dividing into three slender tendons

  • Insertion:

    • Medial tendon: Joins the tendon of the extensor hallucis longus to the base of the proximal phalanx of the great toe (sometimes forming the extensor hallucis brevis)

    • Lateral three tendons: Blend with the extensor digitorum longus tendons of the 2nd, 3rd, and 4th toes on the dorsum of the foot

Tendon Attachments

  • The tendons of EDB cross the dorsum of the foot deep to the superior and inferior extensor retinacula

  • Insert into the dorsal digital expansions of the lateral four toes (usually 2nd–4th)

  • May vary anatomically; in some individuals, a fourth slip reaches the little toe or joins EDL tendons more proximally

Relations

  • Superiorly: Tendons of extensor digitorum longus and extensor hallucis longus

  • Inferiorly: Dorsum of the foot, calcaneus, and tarsal bones

  • Medially: Deep peroneal nerve and dorsalis pedis artery

  • Laterally: Extensor digitorum longus muscle and peroneus tertius tendon

Nerve Supply

  • Deep fibular (peroneal) nerve (L5–S1), a branch of the common fibular nerve

Function

  • Extension of toes: Extends the 2nd, 3rd, and 4th toes at the metatarsophalangeal joints

  • Assists long extensors: Works with the extensor digitorum longus to produce full toe extension

  • Stabilization: Aids in maintaining toe alignment during gait and balance

  • Clinical importance: Weakness or paralysis occurs in deep fibular nerve palsy, contributing to “foot drop”

Clinical Significance

  • Muscle strain or tear: May occur in athletes and dancers during forceful dorsiflexion or jumping

  • Accessory muscle variant: Can mimic a soft-tissue mass on the dorsum of the foot

  • Tendinopathy or tenosynovitis: Presents as dorsal midfoot pain and swelling

  • Nerve injury: Weakness of EDB is an early sign of deep fibular nerve entrapment

  • Imaging relevance: Important for differentiating traumatic tears, accessory slips, and soft-tissue tumors

MRI Appearance

  • T1-weighted images:

    • Muscle belly: intermediate signal intensity

    • Tendons: low signal (dark) coursing over dorsum of foot

    • Fat planes between tendons and muscle are bright and distinct

    • Chronic atrophy shows increased intramuscular fat (hyperintense on T1)

  • T2-weighted images:

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

    • Normal tendon: uniformly low signal

    • Pathology: hyperintense signal within tendon or muscle (strain, edema, partial tear)

    • Denervation: increased signal intensity with mild swelling in early phase

  • STIR:

    • Normal muscle: intermediate-to-dark signal

    • Pathology: bright hyperintensity indicates muscle edema, inflammation, or acute denervation

    • Chronic denervation: reduced volume and dark fibrofatty replacement

  • Proton Density Fat-Saturated (PD FS):

    • Normal tendon: dark, homogeneous appearance

    • Muscle: intermediate-to-dark

    • Tendonitis or partial tear: bright signal areas in tendon or myotendinous junction

    • Useful for subtle peritendinous inflammation and sheath fluid

  • T1 Fat-Sat Post-Contrast:

    • Normal muscle: mild uniform enhancement

    • Tendinitis or synovitis: focal enhancement along tendon sheath

    • Acute denervation: diffuse enhancement of muscle; chronic stage: atrophy and minimal enhancement

CT Appearance

Non-Contrast CT:

  • EDB muscle: well-defined soft-tissue mass on dorsum of foot lateral to EHL tendon

  • Tendons: linear soft-tissue densities blending with EDL tendons

  • Chronic strain or calcific tendinopathy may show linear calcification or thickening along tendon course

  • Muscle atrophy: decreased bulk and attenuation

Post-Contrast CT (standard):

  • Muscle enhances uniformly

  • Inflamed or hypertrophic EDB tendons show focal enhancement

  • Denervated or atrophic muscle: poor enhancement, replaced by low-density fat

  • CT helps delineate ossified or calcified tendinopathy and postoperative changes

MRI image

Extensor digitorum brevis tendons of the Foot axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Extensor digitorum brevis tendons of the Foot axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI image

Extensor digitorum brevis tendons of the Foot axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

MRI image

Extensor digitorum brevis tendons of the Foot axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00003

MRI image

Extensor digitorum brevis tendons of the Foot axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00004

MRI image

Extensor digitorum brevis tendons of the Foot axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00005

CT image

Extensor digitorum brevis tendons ct axial image

CT image

Extensor digitorum brevis tendons ct