Second Palmar Interosseous (Hand)

Origin, Insertion, Action & Nerve

Attachments explained

The Second Palmar 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.

Action & function

When the Second Palmar Interosseous (Hand) contracts, it produces the following movements: Adducts the ring finger toward the axial line of the hand (PAD); 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 Palmar 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 Palmar Interosseous (Hand), impairing the movements it normally produces (adducts the ring finger toward the axial line of the hand (PAD)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Second Palmar Interosseous (Hand) (the OIANS method)

Apply PAD (Palmar ADduct): this muscle draws the ring finger back toward the middle-finger axis. Its unipennate origin from the palmar side of the fourth metacarpal places it to pull that finger inward, opposing the fourth dorsal interosseous.

Fit it into the antagonistic-pairs scheme of the interossei rather than memorising it alone, and reuse the shared facts: deep ulnar nerve supply and the combined action of flexing the metacarpophalangeal joint while extending the interphalangeal joints through the extensor expansion.

Frequently asked questions

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