Second Dorsal Interosseous (Hand)
Hand · Upper Limb
The second dorsal interosseous is a bipennate muscle arising from the adjacent sides of the second and third metacarpals and inserting into the extensor expansion and base of the proximal phalanx of the middle finger on its radial side. It abducts the middle finger toward the thumb side (radially) away from the hand's axial line, following the DAB rule for dorsal interossei, and it flexes the metacarpophalangeal joint while extending the interphalangeal joints. It is supplied by the deep branch of the ulnar nerve (C8, T1).
Origin, Insertion, Action & Nerve
Origin
Adjacent sides of the 2nd and 3rd metacarpals (bipennate)
Insertion
Extensor expansion and base of proximal phalanx of the middle finger (radial side)
Action
Abducts the middle finger radially away from the axial line of the hand (DAB); flexes MCP and extends IP joints
Nerve
Deep branch of ulnar nerve (C8, T1)
Attachments explained
The Second Dorsal Interosseous (Hand) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Adjacent sides of the 2nd and 3rd metacarpals (bipennate)
Insertion
Extensor expansion and base of proximal phalanx of the middle finger (radial side)
Action & function
When the Second Dorsal Interosseous (Hand) contracts, it produces the following movements: Abducts the middle finger radially away from the axial line of the hand (DAB); flexes MCP and extends IP joints.
As part of the Hand group of the Upper Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Second Dorsal Interosseous (Hand) receives its nerve supply from the Deep branch of ulnar nerve (C8, T1). This nerve carries fibres from spinal segment(s) C8, T1.
Because a muscle can only contract when its nerve is intact, injury to the Deep branch of ulnar nerve or to its spinal roots (C8, T1) can weaken or paralyse the Second Dorsal Interosseous (Hand), impairing the movements it normally produces (abducts the middle finger radially away from the axial line of the hand (DAB)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Second Dorsal Interosseous (Hand) (the OIANS method)
Apply the DAB rule (Dorsal ABduct) with the twist that the middle finger is the axis, so this muscle pulls the middle finger toward the thumb side, its radial side. Because the axial line runs through the middle finger itself, abduction here means moving that finger away from centre in one direction.
Learn it as one of the pair that gives the middle finger movement in both directions, alongside the third dorsal interosseous on the other side. Its deep ulnar nerve supply and its combined action, flexing the knuckle while straightening the finger joints, are shared by every interosseous, so reinforce that common pattern.
Frequently asked questions
Where is the Second Dorsal Interosseous (Hand) located?
The Second Dorsal Interosseous (Hand) is a muscle of the Hand group, located in the Upper Limb.
What is the origin of the Second Dorsal Interosseous (Hand)?
Adjacent sides of the 2nd and 3rd metacarpals (bipennate)
What is the insertion of the Second Dorsal Interosseous (Hand)?
Extensor expansion and base of proximal phalanx of the middle finger (radial side)
What movements does the Second Dorsal Interosseous (Hand) produce?
Abducts the middle finger radially away from the axial line of the hand (DAB); flexes MCP and extends IP joints
What nerve supplies the Second Dorsal Interosseous (Hand)?
Deep branch of ulnar nerve (C8, T1)
Is the Second Dorsal Interosseous (Hand) free to study in OIANS?
Yes. The Second Dorsal Interosseous (Hand) is free in OIANS: its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory, and because it belongs to the Upper Limb it is also covered by the free Quiz and Flashcard decks. The other regions, the "All Muscles" deck, and the Progress and Explore tools are unlocked with a one-time Lifetime purchase.
Related muscles
Study the Second Dorsal Interosseous (Hand)
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