Hand & Wrist
The human hand is made up of the wrist, palm, and fingers and consists of 27 bones, 27 joints, 34 muscles, over 100 ligaments and tendons, and many blood vessels and nerves.
The hands enable us to perform many of our daily activities such as driving, writing and cooking. It is important to understand the normal anatomy of the hand to learn more about diseases and conditions that can affect our hands.
Bones of the Hand
The wrist is comprised of 8 carpal bones. These wrist bones are attached to the radius and ulna of the forearm to form the wrist joint. They connect to 5 metacarpal bones that form the palm of the hand. Each metacarpal bone connects to one finger at a joint called the metacarpophalangeal joint (MCP joint). This joint is commonly referred to as the knuckle joint.
The bones in our fingers and thumb are called phalanges. Each finger has 3 phalanges separated by two interphalangeal joints, except for the thumb, which has only 2 phalanges and one interphalangeal joint.
The first joint close to the knuckle joint is called the proximal interphalangeal joint (PIP joint). The joint closest to the end of the finger is called the distal interphalangeal joint (DIP joint).
The MCP and PIP joint act like hinges when the fingers bend and straighten.
Soft Tissues of the Hand
Our hand bones are held in place and supported by various soft tissues. These include: articular cartilage, ligaments, muscles and tendons.
Articular cartilages are smooth material that act as shock absorbers and cushion the ends of bones at each of the 27 joints, allowing smooth movement of the hand.
Muscles and ligaments function to control the movement of the hand.
Ligaments are tough rope-like tissues that connect bones to other bones, holding them in place and providing stability to the joints. Each finger joint has two collateral ligaments on either side, which prevents the abnormal sideways bending of the joints. The volar plate is the strongest ligament in the hand. It joins the proximal and middle phalanx on the palm side of the joint and prevents backward bending of the PIP joint (hyperextension).
Muscles of the Hand
Muscles are fibrous tissues that help produce movement. They work by contracting.
There are two types of muscles in the hand:
- Intrinsic muscles are small muscles that originate in the wrist and hand. They are responsible for fine motor movements of the fingers during activities such as writing or playing the piano.
- Extrinsic muscles that originate in the forearm or elbow control the movement of the wrist and hand. These muscles are responsible for gross hand movements. They position the wrist and hand while the fingers perform fine motor movements.
Each finger has six muscles controlling its movement: three extrinsic and three intrinsic muscles. The index and little finger each have an extra extrinsic extensor.
Tendons of the Hand
Tendons are soft tissues that connect muscles to bones. When muscles contract, tendons pull the bones, causing the finger to move. The extrinsic muscles are attached to finger bones through long tendons that extend from the forearm through the wrist. Tendons located on the palm side help in bending the fingers and are called flexor tendons, while tendons on top of the hand called extensor tendons help in straightening the fingers.
Nerves of the Hand
Nerves of the hand carry electrical signals from the brain to the muscles in the forearm and hand, enabling movement. They also carry the senses of touch, pain and temperature back from the hands to the brain.
The three main nerves of the hand and wrist include:
- Ulnar nerve: The ulnar nerve crosses the wrist through an area called Guyon’s canal and branches to provide sensation to the little finger and half of the ring finger.
- Median nerve: The median nerve crosses the wrist through a tunnel called the carpal tunnel. The median nerve provides sensation to the palm, thumb, index finger, middle finger and part of the ring finger.
- Radial nerve: The radial nerve runs down the thumb side of the forearm and provides sensation to the back of the hand from the thumb to the middle finger.
All three nerves originate at the shoulder and travel down the arm to the hand. Each of these nerves has sensory and motor components.
Blood Vessels of the Hand
Blood vessels travel beside the nerves to supply blood to the hand. The main arteries are the ulnar and radial arteries, which supply blood to the front of the hand, fingers, and thumb. The ulnar artery travels next to the ulnar nerve through the Guyon’s canal in the wrist. The radial artery is the largest artery of the hand, traveling across the front of the wrist, near the thumb. Pulse is measured at the radial artery.
Other blood vessels travel across the back of the wrist to supply blood to the back of the hand, fingers and thumb.
Bursae of the Hand
Bursae are small fluid-filled sacs that decrease friction between tendons and bone or skin. They contain special cells called synovial cells that secrete a lubricating fluid.
Arthritis is an inflammatory condition of the joints. There are several types of arthritis. The most common type is osteoarthritis or wear-and-tear arthritis that affects the joint at the base of the thumb. Thumb arthritis is more common in women than men, and usually occurs after the age of 40 years.
Arthritis is an inflammatory condition of the joints. There are several types of arthritis and the most common type is osteoarthritis or wear-and-tear arthritis. Arthritis affects various joints in the body and the arthritis in the hand affects the joint at the base of the thumb. Arthritis may also affect the joints of other digits.
Arthritis is an inflammatory condition of one or more joints in your body. Triscaphoid joint arthritis is the localised pain and inflammation of the shared joint between the 3 carpal bones of your wrist. These bones are called scaphoid, trapezium, and trapezoid and are present at the base of your thumb.
The bones of the hand are called metacarpals and the bones of the fingers are called phalanges. The metacarpophalangeal joint or MP joint, also known as the first knuckle, is the large joint in the hand where the finger bones meet the hand bones. The MCP joint acts as a hinge joint and is vital during gripping and pinching.
Distal radioulnar joint (DRUJ) arthritis is an inflammatory condition characterized by gradual wearing away of the cartilaginous surface of the radioulnar joint resulting in significant pain, swelling, stiffness, and interference in the functioning of the wrist and/or arm.
Tendons are bands of tissue connecting muscles to bones. The extensor tendon is a strong, smooth cord that connects finger bones to muscles in the hand. Extensor tendons are located just under the skin, directly on the bone, on the back of the hand and fingers. They allow you to open your hands and move or straighten your wrist, fingers, and thumb.
A fingertip injury is a wound or damage caused to the most distal portion of the finger. It can be a crush, a sharp cut, a tear or a combination of these, and can result in damage to the skin, nail or nailbed, tendon, pulp, bone, and nerve endings. It is one of the most common injuries to the hand and may occur due to accidents at home, work, or play.
Carpal instability is the loss of alignment of the carpal bones and/or radioulnar joint. The wrist is a complex joint that connects the forearm to the hand and allows it to move. It consists of 8 small bones called carpals that articulate with two long bones of the forearm (radius and ulna).
Triquetrolunate instability is the instability that takes place between the triquetrum or medial column and the lunate bones or the central column of the wrist. The triquetrum and the lunate comprise the ulnar side of the proximal carpal row at the wrist. This joint is supported by the lunotriquetral (LT) ligament.
A ligament is a strong, flexible band of fibrous tissue. The wrist has many ligaments that help to keep the wrist bones in proper position providing stability to the joint. A torn ligament causes the wrist bones to move out of their position, which in turn leads to wrist instability as the sprained (torn) ligament can no longer support the wrist bones.
A fracture is a break in the bone, which occurs when force greater than the bearable limit is applied against a bone. The most common symptoms of any fracture include severe pain, swelling, bruising or bleeding, deformity and discoloration of the skin and limited mobility of the hand.
The scaphoid bone is a small, boat-shaped bone in the wrist, which, along with 7 other bones, forms the wrist joint. It is present on the thumb side of the wrist, and is at a high risk for fractures. A scaphoid fracture is usually seen in young men aged 20 to 30 years. They can occur at two places: near the thumb or near the forearm.
The forearm is made up of 2 bones, namely, the radius and ulna. The primary function of your forearm is rotation i.e., the ability to turn your palm up and down. The fracture of the forearm affects the ability to rotate your arm, as well as bend and straighten the wrist and elbow. The breaking of the radius or ulna in the middle of the bone requires a strong force and is most commonly seen in adults.
A boxer’s fracture is a break in the neck of the fifth metacarpal bone of the hand (below the pinky finger) close to the knuckle. The hand is composed of 3 types of bones: carpal or wrist bones, metacarpals or long hand bones, and phalanges or finger bones. Metacarpals consist of five long bones that connect the carpal with the phalanges. Structurally, metacarpal bones can be divided into four parts: base, shaft, neck, and head.
Bennet’s fracture is a break at the base of the first metacarpal bone (thumb bone) that meets the wrist at the first carpometacarpal (CMC) joint. The hand is composed of 3 types of bones: carpals or wrist bones, metacarpals or long hand bones, and phalanges or finger bones. Metacarpals consist of five long bones that connect the carpals with the phalanges.
The radius (bone on the thumb side) and ulna (bone on the little-finger side) are the two bones of the forearm. Forearm fractures can occur near the wrist, near the elbow or in the middle of the forearm. Apart from this, the bones in children are prone to a unique injury known as a growth plate fracture.
Injuries that involve tearing or stretching of the ligaments of your fingers are termed as sprains. Sprains in the fingers are most often caused from a fall when you extend your arms to reduce the impact of the fall, or from overuse or repetitive activity of the thumb such as with texting.
Distal intersection syndrome also referred to as tenosynovitis of the radial wrist extensors is characterized by the radial wrist and forearm pain. Distal intersection syndrome is tenosynovitis of the third extensor compartment (extensor pollicis longus) where it crosses the second extensor compartment.
Ganglion cysts are swellings that most commonly develop along the tendons or joints of wrists or hands. They can be found either at the top of the wrist, palm side of the wrist, end joint of a finger or at the base of a finger. A ganglion cyst is not cancerous and will not spread to the other parts of the body.
Tendons in your fingers connect the finger bones to finger muscles and help bend and straighten the finger at the joint when the muscles contract. Boutonnière deformity is a condition in which a tendon injury to the middle joint of the finger results in the inability to straighten the affected finger.
Inflammation and swelling of the tendon sheaths put pressure on the adjacent nerves and leads to pain and numbness in the thumb side of the wrist. Strain on these tendons can cause swelling and irritation, and lead to a condition called De Quervain's tenosynovitis, which is characterized by inflammation.
Dupuytren’s contracture is a hand condition where thickening of the underlying fibrous tissues of the palm causes the fingers to bend inward. This makes it difficult to fully straighten the affected fingers. It commonly occurs in the ring finger and little finger. Occasionally, the middle finger is affected, but the thumb and index finger are rarely affected.
Inflammation in the tenosynovium leads to a condition called trigger finger, also known as stenosing tenosynovitis or flexor tendonitis, where one of the fingers or thumb of the hand is caught in a bent position. The affected digit may straighten with a quick snap, like pulling and releasing the trigger on a gun, hence the name trigger finger.
The hand and wrist are formed during the 8th week of gestation. This process consists of various steps and failure in any one or more of these steps may cause congenital or birth defects. The deformities may be major (absence of a bone) or minor (disproportion of a finger).
Skier's thumb, also known as, Gamekeeper's thumb is a tear of the ulnar collateral ligament, a band of tissue that supports the joint at the base of the thumb. Damage to the ulnar collateral ligament may lead to chronic instability of the thumb, creating problems in its normal functioning.
The finger joint is a hinge joint that allows the bending and straightening of the fingers. Each finger is composed of 3 phalange bones joined by 2 interphalangeal joints (IP joints). The joint near the base of the finger is called the proximal IP joint (PIP joint), and the joint near the tip of the finger is called the distal IP joint (DIP joint).
The wrist is a complex joint made up of 8 carpal bones aligned in two rows, with four bones present in each row. The carpal bones are further connected to 5 metacarpal bones that form the palm of the hand. Each small bone forms a joint with the bone next to it. Thus, the wrist joint is made up of many small joints.
The triangular fibrocartilage complex, or TFCC, is a complex of cartilage and ligaments located near the outer region of the wrist, below the little finger. It serves to stabilize the wrist, allowing easy movement and shock-absorption. Sports activities or falls can damage or injure the TFCC, causing wrist pain and instability.
The wrist is a complex joint made up of 8 carpal bones aligned in two rows with four bones present in each row. The carpal bones are further connected to 5 metacarpal bones that form the palm of the hand. Each small bone forms a joint with the bone next to it. Thus, the wrist joint is made up of many small joints.
The peripheral nerves are the nerve fibers that compose the area from head to toe, connecting the brain and spinal cord with the rest of the body parts. Nerves transmit electrical impulses and signals to and from the brain. Peripheral nervous system disorders interrupt the transmission of signals and weaken the sensory and motor nerve functions.
Sports injuries are injuries that most commonly occur during sports and exercises. These injuries may result from accidents, poor training practices, and use of improper protective gear, lack of conditioning, and insufficient warm-up and stretching. The sports injuries may be either acute (sprains, fractures, tears) or chronic (tendinitis, overuse injury) injuries.
The hand is one of the most flexible and useful parts of our body. Because of overuse in various activities, the hands are more prone to injuries, such as sprains and strains, fractures and dislocations, lacerations and amputations while operating machinery, bracing against a fall and sports-related injuries.
Arthritis is an inflammatory condition of the joints. There are several types of arthritis; the most common type is osteoarthritis or wear-and-tear arthritis that affects the joint at the base of the thumb. Thumb arthritis is more common in women than men, and usually occurs after the age of 40 years.
The carpal tunnel is a narrow passageway on the palm side of your wrist. Small wrist bones known as carpals form the bottom and sides of the carpal tunnel and a strong band of connecting tissue, known as the transverse carpal ligament, covers the top of the carpal tunnel.
The hand is one of the most flexible and useful parts of our body that enable us to perform many of our daily activities. The hands and wrists are prone to injuries or certain orthopedic conditions and can range from minor cuts or burns to severe arthritis or injuries of nerves, bones, and tendons.