Logan Steele
Radial deviation is the tilting of the hand and wrist toward the thumb and radius. This movement is important for weight-bearing activities and plays a crucial role in hand and wrist function, enabling tasks such as grasping, gripping, and manipulating objects. The muscles that control radial deviation are primarily located in the forearm, with the main muscles being the flexor carpi radialis and the extensor carpi radialis longus and brevis. These muscles work together to generate the force required for radial deviation, and their contraction is controlled by the radial nerve.
| Characteristics | Values |
|---|---|
| Radial deviation | Tilting the hand and wrist toward the thumb and radius |
| Muscles involved | Flexor Carpi Radialis, Extensor Carpi Radialis Longus, Extensor Carpi Radialis Brevis |
| Function | Radial deviation is important for grasping objects, performing certain sports movements, and playing musical instruments |
| Location of muscles | Forearm |
| Innervation | Radial nerve |
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What You'll Learn
Extensor Carpi Radialis Brevis
The extensor carpi radialis brevis is a fusiform muscle found in the radial (lateral) part of the posterior forearm. It is one of seven superficial extensor muscles of the posterior forearm, along with brachioradialis, extensor carpi radialis longus, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and anconeus.
The extensor carpi radialis brevis is the shortest of the two muscles, with the tendon of the extensor carpi radialis longus accompanying it to the wrist. The muscle courses inferiorly, giving off a long tendon in the middle of the forearm, which descends towards the dorsal hand. The tendon passes through a groove on the posterior surface of the radius, deep to the extensor retinaculum. After traversing the extensor retinaculum space, the tendon inserts into the posterior aspect of the base of the third metacarpal bone.
The extensor carpi radialis brevis originates from the lateral epicondyle of the humerus via the common extensor tendon. This is a common origin shared with the extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris muscles. Some fibres also originate from the lateral intermuscular septum, a thick aponeurosis that covers the muscle itself, and from the radial collateral ligament.
The specific action of the extensor carpi radialis brevis is to extend and abduct the hand at the wrist joint. It works together with the extensor carpi ulnaris and extensor carpi radialis longus to extend the hand at the wrist joint. The extensor carpi radialis brevis is innervated directly by the radial nerve (C5-C8) or, sometimes, from its deep branch/posterior interosseous nerve. The radial nerve stems from the posterior cord of the brachial plexus.
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Extensor Carpi Radialis Longus
The extensor carpi radialis longus is a muscle that can be found in the posterior compartment of the forearm. It is one of the five main muscles that control movements at the wrist. It is quite long, starting on the lateral side of the humerus and attaching to the base of the second metacarpal bone (metacarpal of the index finger). It is a wrist extensor and can be palpated infero-posteriorly to the elbow.
The extensor carpi radialis longus is one of three primary wrist extensors. It is most effective as a wrist extensor when the elbow is extended and when radial deviation is balanced by the primary ulnar deviator—extensor carpi ulnaris. Functionally, the wrist extensors work strongly in the action of gripping, together with extensor carpi ulnaris. By keeping the wrist in extension, flexion of the wrist by flexors digitorum superficialis and profundus is prevented, with the result that these muscles act on the fingers. When the wrist then moves into flexion, the flexor tendons are unable to shorten enough to generate effective movement at the interphalangeal joints, resulting in a state of active insufficiency.
The extensor carpi radialis longus is also involved in radial deviation, which is the tilting of the hand and wrist toward the thumb and radius. It works together with flexor carpi radialis to cancel flexion and extension, instead pulling the hand toward the radius. This motion is important in weight-bearing activities such as those performed on the balance beam, rings, pommels, and p-bars when using the wrists to maintain an inverted position.
The majority of the extensor carpi radialis longus originates from the lateral supracondylar ridge of the humerus (distal third) and the anterior aspect of the lateral intermuscular septum of the arm. A small portion of its fibres originate from the common extensor tendon attached to the lateral epicondyle of the humerus. The fibres unite into a muscle belly that extends approximately to the middle of the forearm. The muscle belly is then replaced by a flat tendon that travels distally along the lateral surface of the radius.
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Flexor Carpi Radialis
The flexor carpi radialis (FCR) is a muscle of the human forearm that acts to flex and radially abduct the hand. The Latin 'carpus' means wrist; hence, flexor carpi is a flexor of the wrist. This muscle is one of four muscles in the superficial layer of the anterior compartment of the forearm.
The FCR is a fusiform muscle located in the anterior forearm. It is a relatively thin muscle found on the anterior part of the forearm. It arises in the humerus epicondyle, close to the wrist area. The FCR originates from the medial epicondyle of the humerus, via the common flexor tendon, and surrounding fascia. This common flexor tendon is a common origin for the six long flexor muscles in the forearm. From the medial epicondyle, the muscle belly courses obliquely, crossing from the ulnar to the radial part of the forearm.
The FCR inserts at the bases of the second and third metacarpal bones. The tendon of the FCR is visible on the anterior surface of the forearm, just proximal to the wrist, when the wrist is flexed. It is the tendon seen most lateral, closest to the thumb. The FCR is innervated by the median nerve, specifically by axons from cervical nerve roots C6 and C7. The FCR is mostly supplied by a branch arising high in the forearm from the anterior or posterior recurrent ulnar arteries. The rest of its nutritional needs are fulfilled by 6-8 branches of the radial artery.
The FCR has been suggested to act as a dynamic scaphoid stabilizer. The FCR tendon uses the scaphoid tuberosity as a pulley to reach its distal insertion onto the second metacarpal. It has been hypothesized that FCR muscle contraction generates a dorsally directed vector that resists the scaphoid from rotating into flexion. The FCR also contributes to pronation as it obliquely crosses the forearm.
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Brachioradialis
The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is a fusiform muscle, widening at the muscle belly and narrowing at its attachment site. The muscle belly is located in the mid-forearm, where a long, flat tendon begins, which then continues to the radius.
The brachioradialis is the most superficial muscle on the radial side of the forearm. It forms the lateral side of the cubital fossa, or elbow pit, and is often fused proximally with the brachialis. It is also known as supinator longus. The muscle is innervated by the radial nerve and is one of only four muscles that receive input directly from this nerve.
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. When the forearm is pronated, the brachioradialis tends to supinate as it flexes, and when the forearm is supinated, 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.
The muscle is used to stabilize the elbow during rapid flexion and extension while in a midposition, such as in hammering. It is synergistic with the brachialis and biceps brachii, and antagonistic to the triceps brachii and anconeus.
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Forearm muscles
The wrist is a complex joint that connects the radius and ulna—the two bones in the forearm—to the carpals in the hand. Radial deviation is the tilting of the hand and wrist toward the thumb and radius. This motion is important for weight-bearing activities such as gymnastics, acrobatics, and yoga, where the wrist is forced into a hyper-extended position.
The muscles that control radial deviation are primarily located in the forearm and work together synergistically to allow for dexterity and movement. The radial musculature consists of three muscles located at the lateral forearm: the extensor carpi radialis longus, the extensor carpi radialis brevis, and the brachioradialis.
The extensor carpi radialis longus and brevis are prime movers in radial deviation. They work together to cancel flexion and extension, instead pulling the hand and wrist toward the radius. These muscles are rather poor flexors of the elbow. Their main function is the extension and abduction (radial deviation) of the wrist joint. The tendon of the extensor carpi radialis brevis is particularly prone to lesions (lateral epicondylitis), causing pain at the lateral part of the elbow and reducing the ability to extend the hand. This condition is commonly referred to as "tennis elbow."
The brachioradialis muscle is a powerful flexor of the elbow, acting most strongly when the forearm is in semi-pronation. It serves as a reference muscle for the nerve roots C5 and C6 through the brachioradialis reflex.
In summary, the forearm muscles that control radial deviation are the extensor carpi radialis longus, extensor carpi radialis brevis, and brachioradialis. These muscles work together to facilitate the movement of the wrist and elbow, allowing for dexterity and weight-bearing capabilities.
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Frequently asked questions
Radial deviation is the tilting of the hand and wrist toward the thumb and radius.
The muscles that control radial deviation are the flexor carpi radialis, and the extensor carpi radialis longus and brevis.
These muscles are located in the forearm, with the flexor carpi radialis on the palmar side, and the extensor carpi radialis longus and brevis on the dorsal side.
These muscles work together to generate the force necessary for radial deviation, allowing the hand to tilt towards the thumb side and enabling a more stable and secure grip.
The tendon of the extensor carpi radialis brevis is particularly prone to lesions (lateral epicondylitis), causing pain at the lateral part of the elbow and a reduced ability to extend the hand. This condition is commonly referred to as "tennis elbow."
