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Brachioradialis muscle

The brachioradialis is a prominent superficial muscle of the lateral forearm, forming the lateral contour between the arm and forearm. It is unique in that, although located in the posterior (extensor) compartment, it acts as a flexor of the forearm at the elbow. The muscle plays an important role in rapid or resisted flexion, particularly when the forearm is in a mid-pronated (neutral) position, such as during a handshake.

It is frequently visible as a surface landmark on the lateral side of the forearm and serves as an important guide to the radial artery and nerve during surgical approaches.

Synonyms

  • Supinator longus

  • Lateral forearm flexor

Origin, Course, and Insertion

  • Origin: Proximal two-thirds of the lateral supracondylar ridge of the humerus and lateral intermuscular septum

  • Course: Descends obliquely along the lateral forearm, forming a thick belly that tapers into a long tendon near the distal forearm

  • Insertion: Lateral surface of the distal radius, proximal to the styloid process

Tendon Attachments

  • The brachioradialis tendon inserts on the lateral aspect of the distal radius, just superior to the radial styloid process.

  • It forms the lateral boundary of the cubital fossa and partially covers the radial artery at this level.

Relations

  • Superficial: Deep fascia and skin of the lateral forearm

  • Deep: Supinator, pronator teres, and radial artery (in distal forearm)

  • Medial: Biceps tendon and pronator teres

  • Lateral: Extensor carpi radialis longus and brachialis (proximally)

  • Posterior: Radial nerve and its branches in the mid-forearm region

Nerve Supply

  • Radial nerve (C5–C6) before its division into superficial and deep branches

Arterial Supply

  • Radial recurrent artery (main supply)

  • Minor contributions from the radial artery and brachial artery via muscular branches

Venous Drainage

  • Accompanying venae comitantes of the radial artery drain the muscle

  • Superficially, small tributaries drain into the cephalic vein along the lateral forearm

Function

  • Forearm flexion: Main function, most efficient when forearm is in a mid-prone (neutral) position

  • Assists in pronation and supination: Brings forearm back to neutral from either extreme

  • Stabilization: Contributes to dynamic stabilization of the elbow during rapid flexion movements

  • Surface landmark: Defines lateral border of the cubital fossa

Clinical Significance

  • Radial nerve injury: Causes weakness of elbow flexion in mid-prone position

  • Tendinopathy: Overuse can lead to lateral forearm pain or distal tendinitis

  • Surgical landmark: Important in forearm approaches to radial artery, nerve, and lateral epicondyle fractures

  • Compartment syndrome: Lies within lateral compartment, may be affected in high-energy trauma

  • Electromyography: Commonly used muscle for testing radial nerve function

MRI Appearance

  • T1-weighted images:

    • Muscle belly: Intermediate signal intensity

    • Tendon: Low signal (dark linear band) attaching to distal radius

    • Surrounding fat: Bright, providing contrast with muscle

    • Pathology: Atrophy shows increased intramuscular fat signal

  • T2-weighted images:

    • Normal muscle: Intermediate-to-low signal, slightly darker than T1

    • Tendon: Low signal, continuous to radial styloid

    • Pathology: Tendinopathy or strain shows focal bright hyperintensity within the tendon or myotendinous junction

  • STIR:

    • Normal muscle: Intermediate-to-dark signal

    • Pathology: Bright hyperintense signal in muscle or tendon (edema, strain, inflammation)

    • Useful for detecting early soft-tissue injury

  • Proton Density Fat-Saturated (PD FS):

    • Normal muscle: Intermediate-to-dark homogeneous signal

    • Abnormal: Bright areas indicating edema, partial tear, or peritendinous inflammation

    • Excellent for identifying subtle tendon pathology or muscle strain

  • T1 Fat-Sat Post-Contrast:

    • Normal muscle: Homogeneous mild enhancement

    • Inflammation or tear: Focal enhancement around myotendinous junction or tendon sheath

    • Chronic tendinosis: Mild patchy enhancement due to vascular proliferation

CT Appearance

Non-Contrast CT:

  • Muscle belly: Soft-tissue density along lateral forearm

  • Tendon: Linear soft-tissue band inserting onto distal radius

  • Excellent for identifying calcification, ossification, or enthesophytes in chronic tendinopathy

  • Defines relationship with radius and radial artery in preoperative planning

Post-Contrast CT (standard):

  • Muscle shows homogeneous enhancement

  • Inflamed or torn regions demonstrate localized enhancement or surrounding soft-tissue swelling

  • Useful in trauma, chronic tendon changes, or myositis ossificans

MRI images

Brachioradialis muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

MRI images

Brachioradialis muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000_00001

MRI images

Brachioradialis muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000_00002

MRI images

Brachioradialis muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000_00003

MRI images

Brachioradialis muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000_00004

CT images

Brachioradialis muscle ct 2

CT images

Brachioradialis muscle ct axial 1

CT images

Brachioradialis muscle ct axial