The Brachioradialis is a superficial forearm muscle located in the lateral forearm. The brachioradialis primarily flexes the forearm at the elbow but also functions to supinate or pronate depending on the rotation of the forearm. The muscle originates along the proximal two-thirds of the lateral supracondylar ridge of the humerus and distally inserts into the lateral surface of the styloid process of the radius. The brachioradialis has unique attachment points compared to other muscles in the body because it originates from the distal end of one bone and inserts into the distal end of another bone. [rx][rx]
Structure of Brachioradialis
The brachioradialis muscle can be palpated in the anterolateral forearm. The brachioradialis originates proximally from the lateral supracondylar ridge of the humerus and inserts distally to the radial styloid process of the radius. Given these attachments, the brachioradialis only crosses the elbow joint. The muscle has a fusiform shape where it widens at the muscle belly and narrows distally to become a thin tendon at its distal insertion point. The brachioradialis contributes to the muscle mass overlying the anterolateral forearm. [rx][rx]
The brachioradialis muscle contributes to the boundaries of the cubital fossa, forming the lateral boundary along with the wrist extensors. The cubital fossa is on the anterior surface of the elbow and contains important structures such as the brachial artery, median nerve, and biceps tendon. [rx]
There are five compartments of the forearm which include the volar superficial, volar deep, dorsal superficial, dorsal deep, and mobile wad. The brachioradialis is located in the mobile wad compartment along with the extensor carpi radialis longus and extensor carpi radialis brevis muscles. [rx]
The brachioradialis primarily acts as a flexor of the elbow. The muscle has been shown to be active during elbow flexion whether the forearm is supinated, neutral, or pronated. The brachioradialis functions to stabilize the forearm during elbow flexion. [rx] When the forearm is supinated the brachioradialis acts as a pronator and when the forearm is pronated the brachioradialis acts as a supinator. [rx] [rx]
Anatomy of Brachioradialis
Brachioradialis
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Origin: lateral supracondylar ridge of humerus and lateral intermuscular septum
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Insertion: styloid process of the radius
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Action: flexion of the forearm
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Innervation: radial nerve
Blood Supply of Brachioradialis
The brachioradialis muscle is supplied by the radial recurrent artery. The radial recurrent artery is a branch of the radial artery below the elbow joint that runs distal to proximal to contribute to the collateral circulation elbow joint. [rx][rx][rx] The superficial venous drainage of the forearm and elbow has many variations. The cephalic vein and the basilic vein ascend the lateral and medial forearm, respectively. In the most commonly seen venous pattern the median cubital vein arising from the cephalic vein which then crosses the antecubital fossa to combine proximally with the basilic vein. The deep veins form paired vessels around the named arteries of the forearm and arm. [rx][rx][rx]
The brachioradialis lymphatic drainage is part of the upper limb lymphatic system, consisting of superficial and deep lymphatic vessels. The superficial lymphatic vessels closely follow the superficial venous vasculature. Part of the superficial lymphatic system follows the basilic vein to drain into the cubital lymph nodes. Lymphatic vessels around the cephalic vein drain to the axillary lymph nodes. The deep lymphatic vessels also drain lymph from the brachioradialis and travel with the deep veins, eventually draining to the axillary lymph nodes. [rx][rx][rx]
Nerves of Brachioradialis
The brachioradialis muscle is innervated by the radial nerve. [rx][rx] The innervation to the brachioradilis muscle includes contributions from spinal nerve roots C5, C6, and C7, although the brachioradialis muscle is primarily innervated by C5 and C6 nerve roots. [rx] The distal portion of the radial nerve lies between the brachioradialis and the brachialis muscles anteriorly. [rx] Distal to the elbow joint the radial nerve splits into superficial and deep branches. The superficial branch of the radial nerve runs distally in the forearm under the brachioradialis and lateral to the radial artery. Distally the superficial radial nerve emerges superficially between the brachioradialis and extensor carpi radialis longus tendons. [rx] In a radial nerve palsy the brachioradialis is one of the first muscles to recover after nerve injury. [rx]
Brachioradialis is innervated by the radial nerve (from the root values C5-C6) that stems from the posterior cord of the brachial plexus.
Function of Brachioradialis
The brachioradialis flexes the forearm at the elbow. When the forearm is pronated, the brachioradialis tends to supinate as it flexes. In a supinated position, it tends to pronate as it flexes. This also assists the biceps brachii.
The brachioradialis is a stronger elbow flexor when the forearm is in a midposition between supination and pronation at the radioulnar joint. When pronated, the brachioradialis is more active during elbow flexion since the biceps brachii is in a mechanical disadvantage.
With the insertion of the muscle so far from the fulcrum of the elbow, the brachioradialis does not generate as much joint torque as the brachialis or the biceps. It is effective mainly when those muscles have already partially flexed at the elbow. The brachioradialis flexes the forearm at the elbow, especially when quick movement is required and when a weight is lifted during slow flexion of the forearm.
The muscle is used to stabilize the elbow during rapid flexion and extension while in a midposition, such as in hammering. The brachioradialis is synergistic with the brachialis and biceps brachii; the triceps brachii and anconeus are antagonistic.[2][3]
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