Palmaris Brevis

Origin, Insertion, Action & Nerve

Attachments explained

The Palmaris Brevis 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 Palmaris Brevis contracts, it produces the following movement: Wrinkles the skin of the hypothenar palm and deepens the cup of the hand, improving grip.

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 Palmaris Brevis receives its nerve supply from the Superficial branch of the 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 Superficial branch of the ulnar nerve or to its spinal roots (C8, T1) can weaken or paralyse the Palmaris Brevis, impairing the movements it normally produces (wrinkles the skin of the hypothenar palm and deepens the cup of the hand, improving grip). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Palmaris Brevis (the OIANS method)

Palmaris brevis is unusual in that it inserts into skin, not bone, so its job is to wrinkle and tighten the skin over the hypothenar side of the palm. Picture it deepening the palm's hollow to improve grip, and its purely cutaneous attachment makes sense.

The reason it matters clinically is protection: by cushioning the skin over the ulnar nerve and vessels as they enter the hand, it shields them. It is supplied by the superficial branch of the ulnar nerve, distinguishing it from the deep-branch hypothenar muscles it lies over.

Frequently asked questions

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