Maximus Gage
The human wrist is a complex joint, allowing a remarkable range of movement. The muscles that enable wrist flexion include the flexor carpi ulnaris, flexor carpi radialis, palmaris longus, and flexor digitorum superficialis. These muscles are located in the forearm, with the flexor carpi ulnaris and flexor carpi radialis working together to cancel out flexion and extension, allowing for radial and ulnar deviation of the wrist. The flexor digitorum superficialis is a key muscle controlling wrist and finger flexion, while the palmaris longus flexes the wrist by tightening the skin and fascia in the palm. The flexor carpi ulnaris and flexor carpi radialis are also prime movers in wrist flexion, with the former also assisting in ulnar deviation.
| Characteristics | Values |
|---|---|
| Wrist Movements | Flexion, Extension, Radial Deviation, Ulnar Deviation, Pronation, Supination |
| Muscles Involved in Flexion | Flexor Carpi Radialis, Flexor Carpi Ulnaris, Palmaris Longus, Flexor Digitorum Superficialis, Flexor Digitorum Profundus, Flexor Pollicis Longus |
| Muscles Involved in Extension | Extensor Carpi Radialis, Extensor Carpi Ulnaris, Extensor Pollicis Longus |
| Muscles Involved in Radial Deviation | Flexor Carpi Radialis, Extensor Carpi Radialis |
| Muscles Involved in Ulnar Deviation | Flexor Carpi Ulnaris, Extensor Carpi Ulnaris |
| Muscles Involved in Pronation | Supinator, Pronator Teres, Pronator Quadratus |
| Muscles Involved in Supination | Supinator |
| Related Muscles | Palmar Intercarpal Ligaments, Interossei Muscles, Dorsal Interossei, Palmar Interossei |
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What You'll Learn
Flexor Carpi Radialis
The flexor carpi radialis (FCR) is a muscle in the human forearm that acts to flex and radially abduct the hand. The Latin root carpus means wrist, hence flexor carpi is a flexor of the wrist. It is a long, thin, fusiform muscle that belongs to the anterior muscle group and lies in the first layer of the superficial layer of the anterior compartment of the forearm. The FCR is one of four muscles in this layer, along with the pronator teres, flexor carpi ulnaris, palmaris longus, and flexor digitorum superficialis muscles. All these muscles share the function of flexing the hand on the wrist, which is why the entire compartment is also called the flexor compartment of the forearm.
The FCR originates from the medial epicondyle of the humerus, via the common flexor tendon, and surrounding fascia (antebrachial fascia and intermuscular septa). This common flexor tendon is a common origin for the six long flexor muscles in the forearm, including the FCR, palmaris longus, flexor carpi ulnaris, pronator teres, flexor digitorum superficialis, and profundus. From the medial epicondyle, the muscle belly courses obliquely, crossing from the ulnar to the radial part of the forearm. In the lower third of the forearm, it gives off a long tendon that passes below the flexor retinaculum into the palmar surface of the hand.
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 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 works together with the flexor carpi ulnaris and palmaris longus to produce a balanced flexion of the hand, i.e., flexion without abduction. However, when it works in synergy with the extensor carpi radialis longus and brevis, the net result of their counteracting forces is a balanced hand abduction.
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Flexor Digitorum Superficialis
The flexor digitorum superficialis is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints. It is located in the anterior compartment of the forearm, where it is the largest muscle. It is sometimes considered the deepest part of the superficial layer of the anterior forearm, and sometimes considered a distinct "intermediate layer". The muscle has two heads, the humeroulnar and radial, and it is between these heads that the median nerve and ulnar artery pass.
The flexor digitorum superficialis has two origin points. The humeroulnar head originates from the medial epicondyle of the humerus via the common flexor tendon, as well as the medial margin of the coronoid process of the ulna. The radial head originates on the anterior oblique line of the shaft of the radius. The muscle then courses distally across the anterior forearm, separating into superficial and deep layers. The superficial layer gives off tendons directed to the third and fourth digits, while the deep layer gives off tendons to the second and fifth digits.
The flexor digitorum superficialis has several functions. Its primary function is the flexion of the middle phalanges of the four fingers (excluding the thumb) at the proximal interphalangeal joints. However, under continued action, it also flexes the metacarpophalangeal joints and the wrist joint. The muscle is also responsible for the skill actions of the fingers.
The flexor digitorum superficialis can be tested by asking a patient to flex the proximal interphalangeal joint of one of the digits from the second to the fifth, while the other three digits are held in extension to inactivate the flexor digitorum profundus.
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Palmaris Longus
The palmaris longus is a long, slender muscle found in the anterior forearm. It extends from the distal humerus to the root of the hand, and is usually present in the superficial volar compartment of the forearm. However, it is considered a vestigial muscle as studies have shown that a significant percentage of the population may be lacking this muscle in one or both forearms. The absence of the palmaris longus does not seem to impact grip strength.
The palmaris longus is innervated by the median nerve and is the most superficial muscle of the superficial forearm flexors. It sits between the flexor carpi radialis and flexor carpi ulnaris muscles, and is superficial to the flexor digitorum superficialis muscle. The muscle has a short inferior course, giving off a long tendon midway down the forearm. The tendon enters the palmar surface of the hand by passing externally to the flexor retinaculum.
The palmaris longus muscle is a weak flexor and assists in wrist flexion and tensioning the palmar aponeurosis. It also helps in tightening and tensing the palmar aponeurosis and acts as an anchor for the skin and fascia of the hand, resisting horizontal shearing forces in the distal direction. Additionally, the palmaris longus may contribute to thumb abduction movements, which are necessary for opening the hand.
The palmaris longus tendon is of significant importance in surgery, particularly in tendon grafts for the wrist. Its length, diameter, and position make it ideal for replacing ruptured tendons without causing functional deformities. The tendon is also used in the correction of claw-finger deformities and opponensplasty, as it is long enough and has parallel tendon fibres.
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Forearm muscles
The wrist is a complex structure of small bones connected by ligaments. The wrist connects the radius and ulna—the two bones in the forearm—to the carpals in the hand. The wrist and hand exhibit a remarkable range of movement, which is key for grasping and interacting with objects.
The muscles of the forearm that act on the wrist and hand are referred to as extrinsic muscles, or external to the hand. Muscles within the wrist and hand are referred to as intrinsic muscles.
The forearm muscles that flex the wrist include the flexor carpi radialis, flexor carpi ulnaris, and palmaris longus. These three muscles originate in the humerus and cross the forearm, extending through the wrist via tendons and inserting into the bones of the hand. The flexor carpi radialis and flexor carpi ulnaris work together to cancel out flexion and extension, instead pulling towards the radius or ulna. This motion is important in weight-bearing activities, such as those performed on the balance beam, rings, pommels, and p-bars.
The other three muscles that flex the wrist are the flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus. These muscles start in the forearm, with the tendons attaching to the phalanges (finger bones). The flexor digitorum superficialis is a key muscle that controls wrist and finger flex. The flexor pollicis longus is a long, deep muscle responsible for flexing the thumb.
The supinator muscle rotates the palm upwards, while the pronator teres and pronator quadratus work in the opposite direction, turning the palm downwards.
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Ulnar deviation
Other autoimmune diseases, such as lupus, scleroderma, polymyositis, and Sjögren's disease, can also result in ulnar deviation through chronic inflammation of connective tissues. Osteoarthritis, the most common form of arthritis, can lead to ulnar deviation due to the breakdown of joint cartilage from overuse or ageing. Psoriatic arthritis, while less common, may also cause ulnar deviation, typically starting from the distal interphalangeal (DIP) joint at the top of the finger and progressing to other joints in the hand and wrist.
Treatment for ulnar deviation focuses on managing symptoms and preventing further deterioration. Diagnosing and addressing the underlying condition is crucial. Anti-inflammatory medications can help control chronic inflammation and reduce swelling and pain. Splints and hand braces provide support, while physical or occupational therapy may be beneficial in improving muscle strength and range of motion. In some cases, surgical procedures may be necessary to repair damaged ligaments.
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Frequently asked questions
There are six main muscles that enable wrist flexion: Flexor Carpi Radialis, Flexor Carpi Ulnaris, Palmaris Longus, Flexor Digitorum Superficialis, Flexor Digitorum Profundus, and Flexor Pollicis Longus.
The Flexor Carpi Radialis muscle works with the Extensor Carpi Radialis to cancel flexion and extension, instead pulling towards the radius. This motion is important in weight-bearing activities such as gymnastics and yoga.
The Flexor Carpi Ulnaris is a long muscle that originates near the elbow and passes through the wrist, attaching to one of the carpal bones in the wrist. It is responsible for flexion and adduction at the wrist.
The Palmaris Longus is a long muscle that originates near the elbow and passes through the wrist, attaching to the base of the hand. It facilitates wrist flexion.
The Flexor Digitorum Superficialis, Flexor Digitorum Profundus, and Flexor Pollicis Longus are the three muscles that start in the forearm and have tendons attaching to the phalanges (finger bones). These muscles contribute to wrist flexion and finger movement.
