Hand Anatomy
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.
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Carpal tunnel syndrome is a common, painful, progressive condition that is caused by compression of the median nerve at the wrist area.
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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.
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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.
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Ganglion cysts are swellings that most commonly develop along the tendons or joints of wrists or hands.
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Dupuytren’s contracture is a hand condition where thickening of the underlying fibrous tissues of the palm causes the fingers to bend inward.
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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.
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The wrist is a commonly injured joint in the body. Problems include sprains and strains as well as fractures that can occur with lifting and carrying heavy objects, while operating machinery, bracing against a fall, or from sports-related injuries.
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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.
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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.
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A break or a crack in the bones of the thumb is known as a thumb fracture. Fractures may occur anywhere on the thumb, but a fracture at the base of the thumb, near the wrist, is considered the most serious.
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Scaphoid fracture occurs due to a fall on an outstretched hand with complete weight falling on the palm. This fracture usually occurs during motor accidents or sports activities.
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The wrist is comprised of two bones in the forearm, the radius and ulna, and eight tiny carpal bones in the palm. The bones meet to form multiple large and small joints.
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Injuries caused due to stretching or tearing of the ligaments in the wrist are called wrist sprains. Sprains can range from mild to severe, based on the extent of injury to the ligament.
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Deep cuts on the under surface of the wrist, hand or fingers can cut and injure the tendon, and make it unable to bend one or more joints in a finger.
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A mallet finger is a condition where the end of the finger is bent and does not straighten.
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Injuries that involve tearing or stretching of the ligaments of your fingers are termed as sprains.
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Finger dislocation is a condition in which the bone of your finger has moved away from its normal position.
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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.
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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.
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The hand is one of the most flexible and useful parts of our body that assist us in most workplace activities. Hand injuries can range from minor cuts or burns to severe injuries.
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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.
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Malunion of a fracture is a condition where the fractured ends of a bone heal in a misaligned position resulting in bone deformity. Malunions may occur in any bone fractures in the body often due to trauma.
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Hand pain is characterized by distress in the joints and tissues of the hand or fingers. Hand pain can be depicted as pulsating, aching, increased warmth, prickling, irritation and inflexibility.
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Any abnormal lump or bump on the hand is considered a hand tumor. Hand tumors can occur on the skin as a mole or a wart, underneath the skin soft tissue or on the bone.
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Wrist arthroscopy is a minimally invasive surgical procedure performed to view, diagnose and treat problems of your wrist joint.
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Wrist joint replacement surgery, also referred to as total wrist arthroplasty, involves the replacement of a severe arthritic wrist joint with an artificial joint made of metal and plastic components.
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Microvascular surgery or microsurgery is a surgical technique for joining or repairing the damaged blood vessels and nerves during reconstructive surgery of body parts.
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Carpal tunnel syndrome is a common, painful, progressive condition that is caused by the compression of the median nerve at the wrist area.
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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.
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The human wrist is made up of small bones joined together by a band of tough fibrous tissue known as ligaments.
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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.
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A hand fracture is a break in one of the bones in the hand, which occurs when force greater than the bearable limit is applied against a bone.
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Wrist fractures are breaks in any of the bones that form your wrist joint.
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Arthritis develops when the cartilage wears-out, resulting in pain, stiffness and inflammation in the joints. It can affect any joint in the body, but the most commonly affected joints are the small joints of the fingers.
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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.
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Finger joint fusion is performed under local or general anesthesia and usually takes about 2 hours to complete. A cut is made over the back of the finger joint and the soft tissues and nerves are carefully moved aside to expose the damaged joint.
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Arthroscopic partial wrist fusion is a minimally-invasive surgery that uses tiny incisions to immobilize selected bones of the wrist. The wrist joint is one of the most complex joints in the human body.
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Hand therapy is a rehabilitation technique recommended to improve the strength and restore functional activity of hands in patients with upper extremity injuries.
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The hand is one of the most flexible and useful parts of our body that enable us to perform many of our daily activities.
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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.
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Total wrist arthrodesis, also known as wrist fusion, is a surgical procedure in which the wrist joint is stabilized or immobilized by fusing the forearm bone (radius) with the small bones of the wrist.