Logan Steele
The wrist is a complex joint made of eight small bones arranged into two rows, connecting the forearm to the hand. The wrist shares muscles with the forearm, which enable its movement. These muscles are connected to the wrist bones by tendons, which are like strong, flexible ropes. The wrist joint is highly mobile, allowing the hand to move in several directions, but this also makes it prone to injury.
| Characteristics | Values |
|---|---|
| Number of bones in the wrist | 8 |
| Number of rows the wrist bones are arranged in | 2 |
| Number of bones in each row | 4 |
| Names of the bones in the proximal row | scaphoid, lunate, triquetrial, pisiform |
| Names of the bones in the distal row | trapezium, trapezoid, capitate, hamate |
| Number of bones in the hand | 19 |
| Names of the bones in the hand | metacarpals, phalanges, sesamoids |
| Number of phalanges in each finger | 3 |
| Number of phalanges in the thumb | 2 |
| Tendons in the wrist | Extensor tendons, flexor tendons |
| Ligaments in the wrist | Volar plate, radial and ulnar collateral ligaments, volar radiocarpal ligaments, dorsal radiocarpal ligaments, ulnocarpal and radioulnar ligaments |
| Types of grip | Power, Precision |
| Muscles that enable wrist movement | Flexor carpi ulnaris, flexor carpi radialis, flexor digitorum superficialis, extensor carpi radialis longus and brevis, extensor carpi ulnaris, extensor digitorum, abductor pollicis longus |
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What You'll Learn
The wrist shares muscles with the forearm
The wrist is a complex joint that connects the radius and ulna (the two bones in the forearm) to the carpals in the hand. It is a hinge between the arm and hand that lets you reposition your hand. The wrist shares muscles with the forearm, and these muscles are often grouped together to allow for the dexterity and movement of these joints.
The muscles in the wrist and forearm work together to help you move your hand and fingers. The wrist extensors comprise a significant component of the posterior forearm musculature. These muscles generally originate on or near the lateral epicondyle and insert on the distal forearm or in the hand. The wrist shares muscles with the forearm, which can be divided into four groups:
- Flexion: Muscles that let you move your wrist down, toward your palm.
- Extension: Muscles that pull your wrist up, like you would to make a “stop” gesture at someone.
- Adduction: Muscles that let you bend your wrist in, toward the centre of your body.
- Abduction: Muscles that let you bend your wrist out, away from the centre of your body.
The wrist and forearm muscles are essential to the fine motor actions of the upper limb, allowing for complex movements of the arm, wrist, and fingers.
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Flexion and extension movements
The wrist is a complex joint made of eight bones arranged into two rows. The wrist shares muscles with the forearm, which allow for various types of movement, including flexion and extension. Flexion movements are those that let you move your wrist downwards, towards your palm. Extension movements, on the other hand, are those that pull your wrist upwards, like when making a "stop" gesture.
Flexor tendons are the tendons that help you flex and curl your fingers, hand, and wrist. The anterior band, also known as the flexor retinaculum, travels across the palmar side of the wrist and forms the "carpal tunnel". This tunnel is supported by the carpal bones and contains all the flexor tendons, the median nerve, and several arteries and veins.
Extensor tendons, on the other hand, help you extend and straighten your fingers, hand, and wrist. The posterior band, or extensor retinaculum, anchors the extensor tendons and supports the posterior structure of the wrist. The wrist extensor muscles originate near the lateral epicondyle and insert into the distal forearm or hand.
The range of motion during flexion and extension is determined by the radiocarpal and midcarpal joints. During maximum flexion, motion is 40% radiocarpal and 60% midcarpal. During maximum extension, motion is 66.5% radiocarpal and 33.5% midcarpal.
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Wrist anatomy and function
The wrist is a complex joint that connects the radius and ulna (the two bones in the forearm) to the carpals in the hand. It is made up of eight bones arranged into two rows. The proximal row, which is the row closest to the forearm, includes the scaphoid, lunate, triquetrium, and pisiform bones. The distal row, which is the farthest row, is composed of the trapezium, trapezoid, capitate, and hamate bones.
The wrist is a hinge between the arm and hand that allows the hand to reposition itself. It acts as a pivot point, capable of moving in almost any direction as the hand reaches and flexes. The wrist shares muscles with the forearm, which enable four types of movement: flexion, extension, adduction, and abduction. Flexion allows you to move your wrist down, toward your palm, while extension pulls your wrist up, like when making a "stop" gesture. Adduction is when you bend your wrist in, toward the center of your body, and abduction is when you bend your wrist out, away from the center of your body.
The wrist is also capable of pronation (turning down) and supination (turning up) due to the proximal radioulnar joint at the elbow and the distal radioulnar joint, which is the point just before the wrist where the radius and ulna connect. The distal radioulnar joint is not a synovial joint but is formed by the interosseous membrane, a thick ligamentous structure.
The hand and wrist are a complex network of bones, muscles, nerves, connective tissue, and blood vessels. There are 19 bones in each hand, grouped by location and function. The metacarpals are the bones in the palm that give it its shape, while the phalanges are the individual bones that make up the segments of the fingers and thumb. Sesamoids are small bones embedded in the tendons, helping them move smoothly. Tendons are like strong, flexible ropes that link muscles to bones. Extensor tendons help extend and straighten the fingers, hand, and wrist, while flexor tendons help with flexing and curling. Ligaments, on the other hand, are like thick rubber bands that help joints move smoothly, protect them from bending too far, and keep them in proper alignment.
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Wrist joints and their versatility
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 eight small carpal bones arranged into two rows of four bones each. The proximal row, closer to the forearm, includes the scaphoid, lunate, triquetrium, and pisiform bones. The distal row, farther from the forearm, is composed of the trapezium, trapezoid, capitate, and hamate bones.
The wrist joint, also known as the radiocarpal joint, is a highly mobile synovial joint that allows the hand to move in several directions. The versatility of movement in the wrist is due to the dozens of small joints that are formed as each small bone articulates with the adjacent bones. This versatility is also enabled by the articular cartilage covering the ends of each bone where they meet in a joint, improving glide and protecting joint integrity.
The wrist shares muscles with the forearm, which produce flexion, extension, adduction, and abduction at the wrist joint. Flexion moves the wrist down toward the palm, while extension pulls the wrist up and back. Adduction bends the wrist inward toward the body, and abduction bends the wrist outward away from the centre of the body.
The wrist joint is prone to injury due to its high mobility. The wrist maintains some stability through its intrinsic and extrinsic ligaments, such as the volar plate ligament, which connects the first two finger bones. The joint capsule of the wrist joint is lined with a synovial membrane that produces synovial fluid to reduce friction between the articulating structures.
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Tendons and ligaments
The wrist is a complex joint made of eight bones arranged into two rows. The wrist is also made up of muscles, nerves, connective tissue, blood vessels, and tendons and ligaments. The wrist shares muscles with the forearm, which allow for movements such as flexion, extension, adduction, and abduction.
Tendons are thick, flexible, collagen cords that link muscles to bones. The wrist and hand have two groups of tendons: extensor tendons and flexor tendons. Extensor tendons help to extend and straighten the fingers, hand, and wrist. Flexor tendons help to flex and curl the fingers, hand, and wrist. Tendons involved in wrist flexion allow for the action of bending the wrist forward or inward and also help in rotating the wrist. Tendons involved in wrist extension enable the action of bending the wrist backward and help move the wrist toward the thumb or little finger. Tendons involved in finger flexion and extension pass by the wrist on their way to the fingers. The tendons of the wrist are surrounded by a synovial membrane, which produces and holds a special fluid that keeps the joint lubricated.
Ligaments are the other type of connective tissue in the wrist and hand. They are like thick rubber bands and help joints move smoothly, protect the joints from bending too far, and keep the joints in proper alignment. There are many ligaments in the hand, including collateral ligaments and volar plates. Collateral ligaments run on the outside edges of the fingers and thumb, protecting the joints from moving too much from side to side. Volar plate ligaments connect the first two finger bones (phalanges) together on each finger.
Wrist injuries are often the result of falling on an outstretched hand. These types of falls can cause sprains, strains, dislocations, fractures, nerve injuries, and/or damage to blood vessels in the wrist. Wrist ligament injuries can be treated with conservative measures such as immobilization, medication, or surgery.
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Frequently asked questions
Yes, the wrist shares muscles with the forearm.
The muscles in the wrist and hand perform two types of grip: power and precision. Power grip is where your grip strength comes from, for example, when picking up a heavy box. Precision grip uses your fingers' ability to meet your thumb to pinch something between them, for example, picking up a pen.
Flexion is produced mainly by the flexor carpi ulnaris and flexor carpi radialis, with assistance from the flexor digitorum superficialis. Extension is produced mainly by the extensor carpi radialis longus and brevis, and extensor carpi ulnaris, with assistance from the extensor digitorum.
Extensor tendons: these help you extend and straighten your fingers, hand, and wrist. Flexor tendons: these help you flex and curl your fingers, hand, and wrist.
The wrist joint, also known as the radiocarpal joint, is a synovial joint in the upper limb that marks the transition between the forearm and the hand. It is a highly mobile joint that allows the hand to move in several directions.
