Brachioradialis
Forearm · Upper Limb
The brachioradialis is a superficial muscle that forms the lateral border of the cubital fossa and the fleshy bulk of the upper forearm. Despite lying in the extensor compartment, it is a flexor: it arises from the lateral supracondylar ridge of the humerus and inserts far distally on the lateral surface of the radius near the styloid process. It flexes the forearm at the elbow and is at its strongest when the forearm is midway between pronation and supination, the position used when lifting a drink or hammering. It is supplied by the radial nerve (C5, C6), and its preserved reflex is a useful sign in cervical nerve root assessment.
Origin, Insertion, Action & Nerve
Origin
Lateral supracondylar ridge of humerus
Insertion
Lateral surface of distal radius (near styloid process)
Action
Flexion of forearm at elbow (strongest in mid-pronation)
Nerve
Radial nerve (C5, C6)
Attachments explained
The Brachioradialis 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 supracondylar ridge of humerus
Insertion
Lateral surface of distal radius (near styloid process)
Action & function
When the Brachioradialis contracts, it produces the following movement: Flexion of forearm at elbow (strongest in mid-pronation).
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 Brachioradialis receives its nerve supply from the Radial nerve (C5, C6). This nerve carries fibres from spinal segment(s) C5, C6.
Because a muscle can only contract when its nerve is intact, injury to the Radial nerve or to its spinal roots (C5, C6) can weaken or paralyse the Brachioradialis, impairing the movements it normally produces (flexion of forearm at elbow (strongest in mid-pronation)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Brachioradialis (the OIANS method)
The brachioradialis is the classic exception to remember: it sits in the extensor compartment and is supplied by the radial nerve, yet it flexes the elbow. Explain that paradox to yourself by its line of pull, running from the humerus down to the distal radius, and it becomes a memorable oddity rather than a confusing one.
Anchor it to a real action: it is strongest with the forearm in mid-position, the grip you use to hammer a nail or raise a glass, sometimes nicknamed the hitchhiker or beer-drinking muscle. Its tendon reflex tests the C5 to C6 roots, giving the muscle a clinical role in localising cervical nerve lesions.
Frequently asked questions
Where is the Brachioradialis located?
The Brachioradialis is a muscle of the Forearm group, located in the Upper Limb.
What is the origin of the Brachioradialis?
Lateral supracondylar ridge of humerus
What is the insertion of the Brachioradialis?
Lateral surface of distal radius (near styloid process)
What movements does the Brachioradialis produce?
Flexion of forearm at elbow (strongest in mid-pronation)
What nerve supplies the Brachioradialis?
Radial nerve (C5, C6)
Is the Brachioradialis free to study in OIANS?
Yes. The Brachioradialis 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 Brachioradialis
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.