Dominic Stone
The elbow joint is a complex hinge joint that allows for significant motion and function, primarily in the form of extension and flexion. Elbow flexion is the action of bending the arm at the elbow joint. The primary muscles responsible for elbow flexion are the biceps brachii, brachialis, and brachioradialis. The biceps brachii are especially unique as they have two distal attachments at the elbow joint. The brachialis is considered a pure flexor of the forearm at the elbow and is the strongest flexor of the elbow in the absence of supination. The radial nerve innervates five muscles that affect the elbow joint, including the brachialis, anconeus, supinator muscle, brachioradialis, and triceps brachii.
| Characteristics | Values |
|---|---|
| Elbow Flexors | Biceps Brachii, Brachialis, Brachioradialis |
| Primary Flexor | Brachialis |
| Secondary Flexor | Pronator Teres |
| Elbow Extensors | Triceps Brachii, Anconeus |
| Elbow Flexion | Bending the arm at the elbow joint |
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What You'll Learn
The brachialis is the primary elbow flexor
The brachialis is the primary flexor of the elbow. It is a muscle in the upper arm that flexes the elbow and is found mainly in the upper arm between the humerus and the ulna. The brachialis is an important flexor muscle of the forearm at the elbow, providing elbow flexion at all physiologic positions. It is considered a pure flexor of the forearm at the elbow and does not provide any supination or pronation of the forearm. The brachialis is located in the anterior compartment of the arm along with the biceps brachii and coracobrachialis. It is deeper than the biceps brachii muscle and acts as the floor of the cubital fossa, also known as the elbow pit. The brachialis originates from the distal anterior humerus and inserts onto the ulnar tuberosity. It is innervated by the musculocutaneous nerve and may also receive additional innervation from the radial nerve.
The brachialis is the prime mover of elbow flexion, generating about 50% more power than the biceps. It is the strongest flexor of the elbow in the absence of supination. To isolate the brachialis muscle, the forearm needs to be in pronation, as the biceps brachii functions as a supinator and flexor. By pronating the forearm, the biceps are put at a mechanical disadvantage. The brachialis has been traditionally described as a single-head muscle, but cadaver assessments have demonstrated that it may have two heads: one superficial and one deep. The superficial head forms the major head, which originates from the anterior mid-shaft humerus and the lateral intermuscular septum, inserting onto the ulnar tuberosity. The deep head forms a smaller muscle that originates from the anterior humerus and the medial intermuscular septum, inserting mainly into an aponeurosis that branches to the ulna.
The brachialis is an alternative donor for tendon transfer procedures, specifically to reconstruct the flexor digitorum profundus and the flexor pollicis longus after brachial plexus injuries. This donor strategy has been shown to achieve "key pinch" and "hook grasp" in patients. To evaluate the strength of the brachialis muscle, the operator puts resistance on the patient's wrist while the patient holds the elbow extended and with the palm forward. The patient then has to flex the elbow without supination, evaluating the flexor muscle strongest at the elbow. The brachialis may be implicated in Erb's palsy if the brachial plexus becomes injured, leading to elbow flexion weakness.
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The biceps brachii is also a flexor
The elbow is a hinge joint that allows movement in one plane, namely the flexion and extension of the forearm. The elbow also enables the wrist to rotate by pivoting the radius around the ulna. The muscles of the elbow work together to perform these movements, providing both strength and flexibility to the arm.
There are seven major muscles in the elbow that enable flexion, extension, or rotation of the forearm. The elbow flexor muscles include the biceps brachii, the brachialis, and the brachioradialis. The biceps brachii is also a flexor and is the longest of these three muscles, running anterior to the humerus from the scapula to the radius. It is found superficial to the brachialis, which is the primary flexor of the elbow.
The biceps brachii is a flexor that not only bends the arm at the elbow joint but also supinates the forearm, allowing the palm of the hand to turn anteriorly. This dual function of the biceps brachii highlights its importance in providing both strength and flexibility to the arm. While the biceps brachii is a significant flexor, it is the brachialis that is the strongest flexor of the elbow, particularly in the absence of supination.
The brachialis muscle is located mainly in the upper arm, between the humerus and the ulna. It has traditionally been described as a single-head muscle, but cadaver studies have revealed that it may have two heads: one superficial and one deep. This anatomical variation has important clinical implications, especially in surgical approaches involving the brachialis muscle. The third flexor muscle of the elbow is the brachioradialis, which is found mostly in the forearm.
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Elbow flexion with a flexed shoulder isolates the brachialis
The elbow is a hinge joint that allows movement in one plane: the flexion and extension of the forearm relative to the upper arm. The elbow is formed by the meeting of three bones: the humerus in the upper arm, and the ulna and radius in the forearm. The muscles of the elbow work together to produce movement at the elbow joint, providing both strength and flexibility to the arm.
There are seven major muscles that enable movement at the elbow joint. The main flexors of the elbow are the biceps brachii, the brachialis, and the brachioradialis. The biceps brachii is a long muscle that runs anterior to the humerus from the scapula to the radius. It functions as a flexor at the elbow, but it also allows for supination of the forearm and turning of the palm. The brachialis is the primary flexor of the elbow and is found in the upper arm between the humerus and the ulna. The brachialis is the strongest flexor of the elbow in the absence of supination. The third flexor muscle of the elbow is the brachioradialis, which runs from the distal end of the humerus to the distal end of the radius.
When the shoulder is flexed, the biceps brachii is taken out of the equation, isolating the brachialis. This is because the biceps brachii crosses the shoulder and elbow joints, whereas the brachialis only crosses the elbow joint. Therefore, elbow flexion with a flexed shoulder isolates the brachialis. This can be useful in manual evaluations of the strength of the brachialis muscle. For this test, the patient holds their elbow extended with the palm facing forward, and the operator puts resistance on the patient's wrist. The patient then attempts to flex the elbow without supination, which isolates the flexor muscle strongest at the elbow.
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Elbow flexors can be used to bring the upper arm closer to the forearm
The elbow is a hinge joint that allows movement in one plane, specifically the flexion and extension of the forearm in relation to the upper arm. The elbow also enables the wrist to rotate by pivoting the radius around the ulna. The muscles of the elbow work together to perform these movements, providing both strength and flexibility to the arm.
There are seven major muscles in the elbow that enable flexion, extension, or forearm rotation. The elbow flexor muscles are those that are involved in bending the arm at the elbow joint. The main elbow flexors are the biceps brachii, the brachialis, and the brachioradialis. The biceps brachii is a long muscle that runs anterior to the humerus from the scapula to the radius. It functions primarily as a flexor at the elbow, but it can also supinate the forearm and turn the palm of the hand anteriorly.
The brachialis is the primary flexor of the elbow and is found mainly in the upper arm between the humerus and the ulna. It is the strongest flexor of the elbow in the absence of supination. The brachialis has traditionally been described as a single-head muscle, but cadaver assessments have revealed that it may have two heads: one superficial and one deep. The deep head forms a smaller muscle that originates from the anterior humerus and the medial intermuscular septum, inserting mainly into an aponeurosis that branches to the ulna.
The third flexor muscle of the elbow is the brachioradialis, which is found mostly in the forearm. It runs from the distal end of the humerus to the distal end of the radius. The pronator teres is considered a secondary flexor. These muscles have a line of force that passes anterior to the elbow's axis of rotation.
In summary, the elbow flexors, including the biceps brachii, brachialis, and brachioradialis, can be used to bring the upper arm closer to the forearm by decreasing the angle between them. These muscles work together to provide strength and flexibility to the arm, allowing for a wide range of movements at the elbow joint.
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The brachialis is a pure flexor
The brachialis is also known as the workhorse of the elbow. It is the primary flexor of the elbow and is found mainly in the upper arm between the humerus and the ulna. It is a large muscle with a large cross-sectional area, providing it with more strength than the biceps brachii and the coracobrachialis. The brachialis muscle is the strongest flexor of the elbow in the absence of supination.
The fibres of the brachialis extend distally to converge on a strong tendon. The tendon inserts onto the tuberosity of the ulna and onto a rough depression on the anterior surface of the coronoid process of the ulna. The brachialis sometimes has an accessory attachment to the radius or the bicipital aponeurosis. The brachialis is an important flexor muscle of the forearm at the elbow and provides elbow flexion at all physiologic positions.
The brachialis can be clinically assessed by palpating the contracting muscle fibres during flexion of the elbow joint against resistance while the forearm is in the semi-prone position. If the muscle cannot be palpated, testing of its function can be used to assess it. This can present as a weakness when flexing the arm against resistance. The brachialis is the main muscle acting in common upper body exercises such as pull-ups and elbow curls. Overuse of the brachialis during such exercises can cause inflammation in the tendon of the muscle, known as brachialis tendonitis.
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Frequently asked questions
The elbow flexor muscles are the biceps brachii, the brachialis, and the brachioradialis. The pronator teres is considered a secondary elbow flexor.
The elbow flexor muscles are involved in bending the arm at the elbow joint. They also have the potential to pronate or supinate the forearm.
The brachialis is the strongest flexor of the elbow in the absence of supination.
