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Extensor digitorum longus tendons

The extensor digitorum longus (EDL) tendons are the terminal extensions of the EDL muscle, located in the anterior compartment of the leg. The muscle arises from the proximal tibia, fibula, and interosseous membrane, dividing distally into four slender tendons that pass beneath the superior and inferior extensor retinacula to reach the dorsum of the foot.

These tendons insert into the dorsal digital expansions of the lateral four toes, functioning as the primary extensors of the second through fifth digits. The EDL tendons are crucial for toe extension, ankle dorsiflexion, and coordinated foot clearance during the swing phase of gait.

Because of their long, superficial course across the ankle, they are susceptible to tendinitis, partial tears, and entrapment, particularly in athletes and individuals with tight footwear or anterior ankle trauma.

Synonyms

  • Tendons of the long extensor of the toes

  • Common extensor tendons of the toes

Origin, Course, and Insertion

  • Origin (muscle): Lateral condyle of the tibia, proximal three-fourths of the anterior surface of the fibula, interosseous membrane, and anterior intermuscular septum

  • Course (tendons): Muscle fibers converge into a common tendon that passes anterior to the ankle joint under the superior and inferior extensor retinacula, then divides into four separate tendons for the lateral four toes

  • Insertion: Each tendon inserts into the dorsal digital expansion (extensor hood) of the 2nd–5th toes — attaching to both the middle and distal phalanges via slips

Tendon Attachments

  • Each EDL tendon divides into three slips:

    • Central slip: Inserts into the base of the middle phalanx

    • Two collateral slips: Merge distally to insert into the base of the distal phalanx

  • The tendons are stabilized by fibrous sheaths on the dorsum of the foot and intertendinous connections linking adjacent tendons

  • Extensor expansions also receive fibers from the extensor digitorum brevis on the dorsum of the foot

Relations

  • Superiorly: Extensor hallucis longus tendon (medially)

  • Inferiorly: Dorsal surface of metatarsals and phalanges

  • Medially: Tibialis anterior tendon

  • Laterally: Peroneus tertius tendon

  • Posteriorly: Anterior tibial vessels and deep fibular nerve

  • Anteriorly: Extensor retinacula of the ankle

Nerve Supply

  • Deep fibular (peroneal) nerve (roots L5–S1)

Function

  • Extension of toes: Extends the lateral four digits at MTP and IP joints

  • Ankle dorsiflexion: Assists tibialis anterior and EHL in lifting the foot

  • Dynamic stabilization: Maintains toe alignment during gait and balance

  • Propulsion control: Coordinates toe extension during push-off and swing phase

Clinical Significance

  • Tendinopathy: Overuse or friction beneath extensor retinaculum causing anterior ankle pain

  • Tear or rupture: May result from lacerations or sports trauma; leads to loss of toe extension

  • Tenosynovitis: Common in tight footwear or repetitive dorsiflexion activities

  • Nerve injury: Deep fibular nerve lesions cause weakness of toe extension and foot drop

  • Post-surgical relevance: Frequently evaluated in tendon transfers and reconstruction procedures

MRI Appearance

  • T1-weighted images:

    • Normal tendon: low signal (dark linear band) extending over dorsum of foot

    • Surrounding muscle: intermediate signal

    • Fat around tendon sheath: bright

    • Tears: discontinuity or localized hyperintensity within tendon substance

  • T2-weighted images:

    • Normal tendon: low signal intensity (dark)

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

    • Pathology: bright hyperintense areas within tendon sheath (tenosynovitis) or tendon (partial tear)

    • Fluid or inflammation around tendon sheath appears as bright halo

  • STIR:

    • Normal tendons: dark linear structures

    • Normal muscle: intermediate-to-dark signal intensity

    • Pathologic: hyperintense changes in sheath or tendon (edema, inflammation, acute tear)

    • Best for detecting early inflammatory changes or fluid collections

  • Proton Density Fat-Saturated (PD FS):

    • Normal tendon: dark, well-defined margins

    • Normal muscle: intermediate-to-dark homogeneous signal

    • Pathology: bright focal or linear signal within tendon or peritendinous region indicating tendinopathy, small tear, or fluid accumulation

  • T1 Fat-Sat Post-Contrast:

    • Normal tendon: minimal or no enhancement

    • Tendinitis or synovitis: linear or peritendinous enhancement

    • Partial tears: enhancement of surrounding soft tissues and tendon edges

    • Complete rupture: non-enhancing tendon gap with peripheral enhancement from granulation tissue

CT Appearance

Non-Contrast CT:

  • Tendons appear as thin soft-tissue density structures on dorsum of the foot

  • Muscle belly visible proximally in anterior compartment

  • Chronic tendinopathy: may show thickened tendon or small calcifications

  • Acute tear: soft-tissue gap or fluid-density collection along tendon course

Post-Contrast CT (standard):

  • Tendons enhance slightly less than surrounding muscle

  • Inflamed or thickened tendon sheath enhances distinctly

  • Useful in identifying postoperative changes, calcific deposits, or synovial thickening

MRI image

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

MRI image

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

MRI image

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

MRI image

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

MRI image

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

CT image

Extensor digitorum longus tendons ct axial image