Extensor Digiti Minimi
Forearm · Upper Limb
The extensor digiti minimi is a slender extensor devoted to the little finger. It arises from the lateral epicondyle of the humerus through the common extensor tendon and its tendon runs to the extensor expansion of the little finger, joining that of extensor digitorum. It extends the little finger at the metacarpophalangeal and interphalangeal joints, allowing it to be raised independently. It is supplied by the posterior interosseous nerve (C7, C8).
Origin, Insertion, Action & Nerve
Origin
Lateral epicondyle of the humerus via the common extensor tendon
Insertion
Extensor expansion of the little finger (joining the extensor digitorum tendon)
Action
Extends the little finger at the metacarpophalangeal and interphalangeal joints
Nerve
Posterior interosseous nerve (C7–C8)
Attachments explained
The Extensor Digiti Minimi 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
Lateral epicondyle of the humerus via the common extensor tendon
Insertion
Extensor expansion of the little finger (joining the extensor digitorum tendon)
Action & function
When the Extensor Digiti Minimi contracts, it produces the following movement: Extends the little finger at the metacarpophalangeal and interphalangeal joints.
As part of the Forearm 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 Extensor Digiti Minimi receives its nerve supply from the Posterior interosseous nerve (C7–C8). This nerve carries fibres from spinal segment(s) C7, C8.
Because a muscle can only contract when its nerve is intact, injury to the Posterior interosseous nerve or to its spinal roots (C7, C8) can weaken or paralyse the Extensor Digiti Minimi, impairing the movements it normally produces (extends the little finger at the metacarpophalangeal and interphalangeal joints). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Extensor Digiti Minimi (the OIANS method)
Learn extensor digiti minimi as the little finger's private extensor, working alongside the shared extensor digitorum. Its name states everything: it extends the smallest digit, and its independent tendon is why you can raise your little finger on its own.
Group it firmly with the other extensors on the posterior interosseous nerve, the theme running through the whole extensor compartment. Pairing it in your mind with extensor indicis, the index finger's private extensor, gives a tidy little-finger-and-index bracketing of extensor digitorum.
Frequently asked questions
Where is the Extensor Digiti Minimi located?
The Extensor Digiti Minimi is a muscle of the Forearm group, located in the Upper Limb.
What is the origin of the Extensor Digiti Minimi?
Lateral epicondyle of the humerus via the common extensor tendon
What is the insertion of the Extensor Digiti Minimi?
Extensor expansion of the little finger (joining the extensor digitorum tendon)
What movements does the Extensor Digiti Minimi produce?
Extends the little finger at the metacarpophalangeal and interphalangeal joints
What nerve supplies the Extensor Digiti Minimi?
Posterior interosseous nerve (C7–C8)
Is the Extensor Digiti Minimi free to study in OIANS?
Yes. The Extensor Digiti Minimi 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 Extensor Digiti Minimi
Test yourself on Upper Limb muscles with interactive quizzes and flashcards in the free OIANS app.
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