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Third metatarsal bone

The third metatarsal bone is the intermediate long bone of the forefoot, located between the second and fourth metatarsals. It forms part of the central ray of the foot, connecting the lateral cuneiform bone proximally to the base of the third toe distally. Structurally, it provides stability and rigidity to the forefoot and assists in weight transmission during gait.

Among the metatarsals, it has a relatively rigid articulation with the lateral cuneiform and is less mobile than the first or fifth metatarsals. This makes it susceptible to stress fractures, particularly in runners and athletes.

Synonyms

  • Third metatarsal

  • Metatarsus III

  • Os metatarsale tertium

Location and Articulations

  • Location: Middle of the metatarsal series in the forefoot, between the second and fourth metatarsals

  • Proximal articulation: Base articulates with the lateral cuneiform

  • Medial articulation: With the second metatarsal base

  • Lateral articulation: With the fourth metatarsal base

  • Distal articulation: With the base of the proximal phalanx of the third toe

Surfaces and Features

  • Base (proximal end): Wedge-shaped, articulating with the lateral cuneiform

  • Shaft (body): Slightly concave plantarward and convex dorsally

  • Head (distal end): Rounded articular surface forming the metatarsophalangeal (MTP) joint

  • Dorsal surface: Smooth for extensor tendon gliding

  • Plantar surface: Gives attachment to interosseous and lumbrical muscles

Attachments

  • Muscular:

    • Dorsal interossei (second muscle): Originates from adjacent sides of the third and fourth metatarsals

    • Plantar interossei (first muscle): Originates from the medial aspect of the third metatarsal shaft

  • Ligamentous:

    • Dorsal, plantar, and interosseous ligaments connecting adjacent metatarsals

    • Deep transverse metatarsal ligament binding heads of the metatarsals together

Relations

  • Superiorly: Extensor tendons and dorsal interossei muscles

  • Inferiorly: Plantar interossei muscles and plantar fascia

  • Medially: Second metatarsal and dorsal interosseous tendons

  • Laterally: Fourth metatarsal and adjacent interossei

Arterial Supply

  • Dorsalis pedis artery: via dorsal metatarsal branches

  • Plantar metatarsal arteries: branches of the deep plantar arch

  • Nutrient artery: usually arises from the dorsal metatarsal artery supplying the shaft and head

Venous Drainage

  • Dorsal venous arch and plantar venous plexus, draining into dorsal metatarsal veins and then into saphenous and posterior tibial veins

Function

  • Weight transmission: Transfers load from the cuneiforms to the toes during stance and push-off

  • Forefoot stability: Central pillar maintaining transverse and longitudinal arches

  • Balance: Assists in even weight distribution across the forefoot

  • Locomotion: Provides leverage during toe-off phase of gait

Clinical Significance

  • Fractures: Stress fractures common in athletes; acute fractures may occur from direct trauma

  • Overuse injuries: Repetitive microtrauma can cause periostitis or stress reaction

  • Infection: Osteomyelitis possible in diabetics or post-trauma

  • Deformities: Can be displaced in forefoot trauma or collapse of the transverse arch

  • Imaging importance: MRI detects early stress changes before radiographs show fracture lines

MRI Appearance

  • T1-weighted images:

    • Normal marrow: bright signal, depending on fat content

    • Cortex: low signal (dark rim)

    • Fracture or marrow edema: low signal replacing normal fatty brightness

    • Tendon and ligament attachments appear dark

  • T2-weighted images:

    • Normal marrow: bright signal, variable based on marrow fat composition

    • Cortex: dark

    • Stress fracture or edema: focal or diffuse hyperintense area within shaft or base

    • Joint cartilage: intermediate-to-bright signal

  • STIR (Short Tau Inversion Recovery):

    • Normal marrow: dark

    • Bone stress reaction, contusion, or fracture: bright hyperintense signal

    • Highlights early inflammatory and edema changes

  • Proton Density Fat-Saturated (PD FS):

    • Normal marrow: dark (suppressed fat signal)

    • Pathology: bright signal representing edema, stress injury, or infection

    • Useful for detecting subtle cortical or periosteal reaction

  • T1 Fat-Sat Post-Contrast:

    • Normal bone: mild homogeneous enhancement

    • Inflammation or osteomyelitis: heterogeneous enhancement

    • Non-enhancing regions correspond to necrosis or sclerotic bone

CT Appearance

Non-Contrast CT:

  • Excellent cortical detail showing fractures, sclerosis, periosteal reaction, or lytic changes

  • Stress fractures: appear as sclerotic lines or cortical breaks

  • Chronic injury: cortical thickening or callus formation

  • Osteonecrosis: mottled sclerosis and collapse of metatarsal head

Post-Contrast CT (standard):

  • Provides limited added value for cortical bone

  • Can show enhancement in infection or active bone remodeling

  • Best used for assessing bony architecture and alignment in fractures

CT VRT 3D image

third Metatarsal Bone ct vrt image

MRI image

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MRI image

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CT image

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CT image

third Metatarsal Bone