Palmaris Longus
Forearm · Upper Limb
The palmaris longus is a slender, often-absent muscle of the anterior forearm, missing in roughly one person in seven. It arises from the medial epicondyle through the common flexor origin and, uniquely, inserts into the flexor retinaculum and palmar aponeurosis rather than onto bone. It weakly flexes the wrist and tenses the palmar aponeurosis, cupping the palm. It is supplied by the median nerve (C7, C8). Because its loss causes no functional deficit, its tendon is a favoured donor for surgical grafts.
Origin, Insertion, Action & Nerve
Origin
Medial epicondyle of humerus (common flexor origin)
Insertion
Flexor retinaculum and palmar aponeurosis
Action
Flexion of wrist; tenses palmar aponeurosis
Nerve
Median nerve (C7, C8)
Attachments explained
The Palmaris Longus 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
Medial epicondyle of humerus (common flexor origin)
Insertion
Flexor retinaculum and palmar aponeurosis
Action & function
When the Palmaris Longus contracts, it produces the following movements: Flexion of wrist; tenses palmar aponeurosis.
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 Palmaris Longus receives its nerve supply from the Median 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 Median nerve or to its spinal roots (C7, C8) can weaken or paralyse the Palmaris Longus, impairing the movements it normally produces (flexion of wrist). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Palmaris Longus (the OIANS method)
Palmaris longus is best learned by its two peculiarities: it is frequently absent, and it inserts into fascia (the palmar aponeurosis) rather than bone. Those facts explain why it is only a weak wrist flexor and why its main effect is tensing the skin of the palm. Test it on yourself by pinching thumb to little finger and flexing the wrist to see the tendon appear, if you have one.
The clinical point that makes it stick is that its absence costs nothing, so surgeons harvest its tendon for grafts. Group it with the other median-nerve superficial flexors, and remember it as the small, dispensable strip running down the middle of the wrist.
Frequently asked questions
Where is the Palmaris Longus located?
The Palmaris Longus is a muscle of the Forearm group, located in the Upper Limb.
What is the origin of the Palmaris Longus?
Medial epicondyle of humerus (common flexor origin)
What is the insertion of the Palmaris Longus?
Flexor retinaculum and palmar aponeurosis
What movements does the Palmaris Longus produce?
Flexion of wrist; tenses palmar aponeurosis
What nerve supplies the Palmaris Longus?
Median nerve (C7, C8)
Is the Palmaris Longus free to study in OIANS?
Yes. The Palmaris Longus 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 Palmaris Longus
Test yourself on Upper Limb muscles with interactive quizzes and flashcards in the free OIANS app.
Quiz yourself → Flashcards Open the OIANS app
Browsing is always free. A one-time Lifetime unlock adds every region's quizzes, flashcards, progress tracking and explore tools.