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The wrist is a complex joint that connects the forearm to the hand, allowing for a wide range of movements. It is made up of a network of bones, muscles, tendons, ligaments, nerves, and blood vessels. The muscles that move the wrist can be categorised into two groups: intrinsic muscles, which provide fine motor movements, and extrinsic muscles, which provide strength. These muscles work together to enable various types of grips and precise movements of the hand and fingers. The wrist shares muscles with the forearm, and the movement of the wrist is also facilitated by tendons and ligaments that connect the muscles to the bones and provide stability.
| Characteristics | Values |
|---|---|
| Number of muscles in the hand | 34 |
| Muscles that move the wrist | Flexor Carpi Ulnaris, Flexor Carpi Radialis, Palmaris longus, Flexor Digitorum Superficialis, Extensor Carpi Radialis Longus, Extensor Carpi Radialis Brevis, Extensor Carpi Ulnaris, Extensor Digitorum, Flexor Carpi Radialis, Extensor Carpi Ulnaris |
| Types of grip | Power, Precision |
| Types of grasp | Power, Cylindrical, Hook, Lateral prehension |
| Types of arches | Longitudinal, Oblique, Transverse |
| Types of motion | Supination (anterior rotation), Pronation (posterior rotation) |
| Types of tendons in the hand and wrist | Extensor, Flexor |
| Types of ligaments in the hand | Collateral, Volar plate, Radial and ulnar collateral, Volar radiocarpal, Dorsal radiocarpal, Ulnocarpal, Radioulnar |
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What You'll Learn
Forearm muscles that cross the carpometacarpal joint
The wrist is a complex joint that connects the radius and ulna (the two bones in the forearm) to the carpals in the hand. The wrist shares muscles with the forearm, and these muscles work together to help you move your hand and fingers.
The carpometacarpal (CMC) joints are the articulations between the carpal bones and metacarpal bones of the hand. There are five CMC joints in total, with the first CMC joint, also known as the trapeziometacarpal joint (TMC), connecting the trapezium to the first metacarpal bone. This joint is crucial for normal thumb functioning and is the most specialised and flexible CMC joint. The remaining four CMC joints are functional plane synovial joints that connect the medial four metacarpal bones with the distal row of carpal bones.
The CMC joints are associated with several soft tissue structures, including tendons and muscles. On the palmar side of the hand, the CMC joints are covered by the tendons of the flexor digitorum superficialis, flexor digitorum profundus, flexor carpi radialis, and flexor carpi ulnaris muscles. The hypothenar muscles also overlay the medial CMC joints. On the dorsal side, the CMC joints are situated deep to the tendons of the extensor carpi radialis longus, extensor carpi radialis brevis, extensor pollicis longus, extensor indicis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris muscles.
The muscles of the forearm that cross the CMC joint can produce flexion or extension at the wrist joint. For example, the oblique opponens digiti minimi muscle of the hand acts on the fifth CMC joint and is the only muscle that acts on the CMC joints independently. It is responsible for flexing and rotating the fifth metacarpal bone. Additionally, the fixed second and third CMC joints are crossed by the radial wrist muscles (flexor carpi radialis, extensor carpi radialis longus, and extensor carpi radialis brevis), which enhance their stability and efficiency.
The CMC joints are innervated by the anterior and posterior interosseous nerves of the forearm, which originate from the median and radial nerves, respectively. The blood supply to the CMC joints comes from the palmar and dorsal carpal anastomotic arches, formed by the union of the radial artery's palmar and dorsal carpal branches.
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Flexor muscles and tendons
The wrist is a complex joint, connecting the radius and ulna in the forearm to the carpals in the hand. The wrist is moved by the muscles in the forearm, which are connected to the wrist by tendons. Tendons are like strong, flexible ropes, linking muscles to bones.
The flexor tendons are divided into five zones based on their anatomical location. Zone I is distal to FDS insertion and contains only the FDP. Zone II contains both the FDS and FDP within a narrow sheath. Zone II is a common site of injury, known as "flexor zone II". Zone III runs from the A1 pulley to the distal edge of the flexor retinaculum.
The flexor retinaculum is a thick band at the wrist that anchors the flexor tendons in place. It travels across the palmar side of the wrist, forming the carpal tunnel, through which the flexor tendons, median nerve, and several arteries and veins pass. The carpal tunnel is a rounded space in the wrist that allows tendons, ligaments, and nerves to reach the hand.
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Extensor muscles and tendons
The wrist is a complex joint that connects the radius and ulna (the two bones in the forearm) to the carpals in the hand. The wrist shares muscles with the forearm, and these muscles work together to help you move your hand and fingers.
The extensor muscles and tendons are involved in the extension movement of the wrist, which involves pulling the wrist up, such as when making a "stop" gesture. The primary muscles involved in this movement include the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris. These muscles act synergistically to produce the extension movement.
The extensor tendon compartments of the wrist are six tunnels that transmit the long extensor tendons from the forearm into the hand. These tunnels are located on the posterior aspect of the wrist and are lined internally by a synovial sheath. The first extensor compartment is located on the lateral (radial) aspect of the wrist and transmits two tendons that form the lateral border of the anatomical snuffbox. The second extensor compartment contains the tendons of the extensor carpi radialis longus and brevis, and the third compartment conducts the extensor pollicis longus tendon, forming the medial border of the anatomical snuffbox. The fourth extensor compartment transmits the tendons of the extensor digitorum and extensor indicis, while the fifth contains the extensor digiti minimi tendon for the little finger. The sixth and final compartment is located on the medial (ulnar) aspect of the wrist and conducts the tendon of the extensor carpi ulnaris.
The extensor tendons play a crucial role in allowing the extension and straightening of the fingers, hand, and wrist. The independent extension of the index finger is facilitated by the extensor indicis proprius muscle, while the extensor digiti minimi muscle enables independent extension of the small finger. The thumb extension is achieved through the action of the abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus muscles.
Injuries to the extensor tendons can occur, with the first and sixth compartments being commonly affected. De Quervain's tenosynovitis, caused by repetitive trauma, results in thickening of the tendons in the first compartment, leading to pain, inflammation, and swelling near the base of the thumb. The sixth compartment can suffer recurrent dislocation due to a tear in the ulnar side, commonly seen in individuals who engage in racket sports and golf.
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Radial deviation
The wrist is a complex joint that connects the radius and ulna (the two bones in the forearm) to the carpals in the hand. The wrist is made up of a series of small joints, tendons, ligaments, and muscles that work together to allow for dexterity and movement.
The muscles involved in radial deviation are the Flexor Carpi Radialis and Extensor Carpi Radialis. These muscles work together to cancel flexion and extension, instead pulling the hand and wrist toward the radius bone.
To strengthen the radial deviation, one can perform exercises such as wrist lifts. Start by keeping your arm straight down by your side. Then, bend your wrist forward to lift a weight, ensuring that only your wrist moves and your arm remains stationary. Hold this position for 5 seconds, or as instructed, and slowly lower your hand back down.
It is important to note that the wrist is a complex joint with many ligaments, tendons, and muscles working together to allow for dexterity and movement. Any pain or discomfort in the wrist should be addressed by a healthcare professional, especially if it is worsening over time.
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Ulnar deviation
The wrist is a complex joint, connecting the radius and ulna (the two bones in the forearm) to the carpals in the hand. The wrist is made up of a network of bones, muscles, nerves, connective tissue, and blood vessels. The carpal tunnel, a space in the wrist, allows nine tendons, four ligaments, and one nerve to pass through it and reach the rest of the hand.
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Frequently asked questions
There are four types of wrist movement: flexion, extension, adduction, and abduction. Flexion is the movement of the wrist towards the palm, while extension is the movement of the wrist backwards, usually used for weight-bearing. Adduction is the movement of the wrist towards the centre of the body, and abduction is the opposite, moving the wrist away from the centre of the body.
The muscles involved in wrist flexion include the flexor carpi ulnaris, flexor carpi radialis, palmaris longus, and flexor digitorum superficialis.
The muscles involved in wrist extension include the extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, and extensor digitorum.
The supinator and pronator teres muscles in the forearm are important for supination (anterior rotation) and pronation (posterior rotation) of the wrist. The flexor retinaculum and extensor retinaculum are also important, anchoring the flexor and extensor tendons, respectively, and providing support to the wrist structure.
