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Second dorsal interosseous muscle of foot

The second dorsal interosseous muscle is one of the four dorsal interossei located in the forefoot between the metatarsal bones. It occupies the intermetatarsal space between the second and third metatarsals and is primarily responsible for abducting the second toe away from the midline of the foot and assisting in flexion at the metatarsophalangeal (MTP) joint.

Each dorsal interosseous muscle is bipennate, arising from adjacent sides of two metatarsals and inserting into the base of the proximal phalanx. The second dorsal interosseous specifically contributes to maintaining forefoot stability, balance, and controlled toe movements during walking and push-off.

Synonyms

  • Second dorsal intermetatarsal muscle

  • Second interosseous dorsalis pedis

Origin, Course, and Insertion

  • Origin: Adjacent sides of the second and third metatarsal shafts

  • Course: Fibers converge toward the second toe, forming a short, thick tendon

  • Insertion: Lateral side of the base of the proximal phalanx of the second toe and the dorsal digital expansion

Tendon Attachments

  • The tendon blends with the dorsal digital expansion of the second toe

  • Inserts on the lateral aspect of the proximal phalanx

  • Works in conjunction with the first dorsal interosseous (which inserts medially on the same toe) to provide bidirectional control of the second digit

Relations

  • Superiorly: Dorsal metatarsal vessels and deep branch of the lateral plantar nerve

  • Inferiorly: Plantar interossei and deep plantar arch

  • Medially: First dorsal interosseous muscle (between 1st–2nd metatarsals)

  • Laterally: Third dorsal interosseous (between 3rd–4th metatarsals)

  • Posteriorly: Deep plantar fascia and extensor tendons of the digits

Nerve Supply

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

Arterial Supply

  • Dorsal metatarsal arteries (from arcuate artery)

  • Contributions from deep plantar arch branches

Venous Drainage

  • Dorsal metatarsal veins, draining into the dorsal venous arch of the foot and then into the great saphenous vein

Function

  • Abduction: Abducts the second toe away from the foot’s midline

  • Flexion: Assists flexion of the MTP joint of the second toe

  • Extension control: Stabilizes proximal phalanx during extension of interphalangeal joints

  • Forefoot stability: Maintains spacing between metatarsal heads, contributing to balance

  • Arch support: Provides minor support to the transverse arch during stance

Clinical Significance

  • Muscle strain: Overuse or trauma may cause dorsal foot pain, especially in runners or dancers

  • Intermetatarsal bursitis: Can irritate the dorsal interosseous region causing swelling or pain between second and third metatarsals

  • Nerve entrapment: Deep branch of lateral plantar nerve or interdigital nerve compression may mimic interosseous pain

  • Surgical relevance: Important landmark in dorsal approaches to the metatarsals and in Morton’s neuroma surgery

  • Imaging role: MRI is gold standard for detecting interosseous muscle pathology, denervation, or soft-tissue lesions

MRI Appearance

  • T1-weighted images:

    • Normal muscle: intermediate signal intensity with distinct fascicular pattern

    • Surrounding fat: bright signal outlining intermetatarsal spaces

    • Atrophy or fatty infiltration: increased signal within muscle belly

    • Tendons and fascia: low signal intensity

  • T2-weighted images:

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

    • Pathology: focal or diffuse bright hyperintense areas indicating edema or muscle strain

    • Chronic denervation: diffuse hyperintensity with muscle volume loss

  • STIR:

    • Normal muscle: intermediate-to-dark signal intensity

    • Edema, inflammation, or ischemia: bright hyperintense signal within the intermetatarsal space

    • Useful for detecting acute myositis or intermetatarsal bursitis

  • Proton Density Fat-Saturated (PD FS):

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

    • Pathologic muscle: bright signal with fuzzy margins due to fluid or inflammatory change

    • Excellent for evaluating muscle strain, perimuscular fluid, or denervation edema

  • T1 Fat-Sat Post-Contrast:

    • Normal muscle: uniform mild enhancement

    • Inflammation or myositis: strong focal or diffuse enhancement

    • Neoplastic lesions or infection: irregular heterogeneous enhancement

CT Appearance

Non-Contrast CT:

  • Muscle belly: soft-tissue density within second intermetatarsal space

  • Intermetatarsal fat: low-density planes separating adjacent muscles

  • Chronic injury or atrophy: decreased bulk and low-density fatty replacement

  • Calcific myositis or ossification: small hyperdense foci within muscle

Post-Contrast CT (standard):

  • Normal muscle: mild, homogeneous enhancement

  • Inflammation or infection: increased focal enhancement

  • Atrophy: reduced volume with minimal enhancement

  • Useful in evaluating post-surgical fibrosis, space-occupying lesions, or intermetatarsal bursitis

MRI images

Second dorsal interosseous muscle of foot muscle coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Second dorsal interosseous muscle of foot CT axial