How many knuckles does a human hand have. What are the main components of hand anatomy. Which joints are responsible for finger movement. How do muscles and tendons work together in the hand. What is the role of nerves in hand function.

The Intricate Structure of the Human Hand

The human hand is a marvel of biological engineering, comprising an intricate network of bones, joints, muscles, tendons, ligaments, blood vessels, and nerves. This complex structure enables us to perform a wide range of tasks, from delicate manipulations to powerful grips. Let’s delve into the fascinating anatomy of the human hand to understand its components and functionality.

Bones and Joints: The Framework of the Hand

The skeletal structure of the hand forms the foundation for its incredible versatility. But how many bones make up this remarkable appendage?

A human hand consists of 27 bones, which can be categorized into three main groups:

• 8 carpal bones in the wrist
• 5 metacarpal bones in the palm
• 14 phalanges in the fingers (3 in each finger, 2 in the thumb)

These bones are connected by 27 joints, allowing for a wide range of motion. The most prominent joints in the hand include:

1. Metacarpophalangeal (MCP) joints: Commonly known as knuckles, these joints connect the metacarpal bones to the phalanges.
2. Proximal interphalangeal (PIP) joints: Located between the first and second phalanges of each finger.
3. Distal interphalangeal (DIP) joints: Found between the second and third phalanges of each finger.

Knuckles: The Visible Joints

When we talk about knuckles, we’re typically referring to the visible bumps on the back of the hand. But how many knuckles does a human hand actually have?

While we commonly think of the four visible knuckles at the base of our fingers, technically, there are 14 knuckles in total on each hand:

• 4 knuckles at the base of the fingers (MCP joints)
• 8 knuckles in the fingers (2 per finger – PIP and DIP joints)
• 2 knuckles in the thumb (MCP and IP joints)

Soft Tissues: Supporting the Hand’s Structure

The bones and joints of the hand are supported and held in place by various soft tissues. These include:

• Articular cartilage: A smooth material that cushions the ends of bones at each joint, allowing for smooth movement.
• Ligaments: Tough, rope-like tissues that connect bones to other bones, providing stability to the joints.
• Muscles: Fibrous tissues that produce movement through contraction.
• Tendons: Soft tissues that connect muscles to bones, translating muscle contractions into bone movement.

Muscles and Tendons: The Power Behind Hand Movement

The hand’s remarkable dexterity is made possible by the intricate interplay of muscles and tendons. How do these tissues work together to control hand movement?

There are two types of muscles in the hand:

1. Intrinsic muscles: Small muscles that originate in the wrist and hand, responsible for fine motor movements.
2. Extrinsic muscles: Larger muscles that originate in the forearm or elbow, controlling gross hand movements and wrist positioning.

Each finger is controlled by six muscles: three extrinsic and three intrinsic. The index and little fingers have an additional extrinsic extensor muscle.

Tendons connect these muscles to the bones, translating muscle contractions into finger movements. There are two main types of tendons in the hand:

• Flexor tendons: Located on the palm side, these help bend the fingers.
• Extensor tendons: Found on the back of the hand, these assist in straightening the fingers.

Nerves: The Hand’s Sensory and Motor Control System

The nervous system plays a crucial role in hand function. But which nerves are responsible for controlling hand movement and sensation?

Three main nerves innervate the hand:

1. Ulnar nerve: Provides sensation to the little finger and half of the ring finger.
2. Median nerve: Supplies sensation to the palm, thumb, index finger, middle finger, and part of the ring finger.
3. Radial nerve: Provides sensation to the back of the hand from the thumb to the middle finger.

These nerves carry electrical signals from the brain to the muscles, enabling movement, and transmit sensory information such as touch, pain, and temperature back to the brain.

Blood Supply: Nourishing the Hand’s Tissues

A robust blood supply is essential for the hand’s proper function. Which blood vessels are responsible for delivering oxygen and nutrients to the hand’s tissues?

The main arteries supplying blood to the hand are:

• Ulnar artery: Travels alongside the ulnar nerve through Guyon’s canal in the wrist.
• Radial artery: The largest artery of the hand, running across the front of the wrist near the thumb. This is where the pulse is typically measured.

Additional blood vessels traverse the back of the wrist to supply blood to the posterior aspect of the hand.

Common Hand Conditions and Injuries

Understanding hand anatomy is crucial for recognizing and treating various hand conditions and injuries. What are some common issues that can affect hand function?

• Carpal tunnel syndrome: Compression of the median nerve as it passes through the carpal tunnel in the wrist.
• Trigger finger: A condition where a finger becomes locked in a bent position due to inflammation of the tendon sheath.
• Arthritis: Inflammation of the joints, which can affect any of the hand’s 27 joints.
• Tendonitis: Inflammation of the tendons, often due to overuse or repetitive motions.
• Fractures: Breaks in any of the hand’s 27 bones, commonly occurring in the metacarpals or phalanges.

Recognizing the intricate anatomy of the hand helps medical professionals diagnose and treat these conditions effectively, ensuring optimal hand function and quality of life for patients.

The Evolution of Hand Anatomy

The human hand’s complex structure is a result of millions of years of evolution. How has our hand anatomy evolved to support our unique capabilities?

The opposable thumb, a defining feature of human hand anatomy, has played a crucial role in our species’ development. This adaptation allows for precise manipulation of objects and tools, setting us apart from other primates. The evolution of our hand structure has been closely linked to the development of our cognitive abilities, enabling us to create and use increasingly complex tools.

Some key evolutionary changes in human hand anatomy include:

• Longer thumbs relative to finger length compared to other primates
• Increased mobility of the thumb and fingers
• Enhanced sensory capabilities through increased nerve endings
• Greater muscular control for fine motor skills

These adaptations have allowed humans to excel in tasks requiring precision and dexterity, contributing significantly to our technological and cultural advancements.

Comparative Anatomy: Human Hands vs. Other Primates

While human hands share many similarities with those of other primates, there are notable differences that reflect our unique evolutionary path. How do human hands compare to those of our closest relatives?

Compared to other primates, human hands exhibit:

1. Shorter fingers and palms relative to overall hand size
2. Greater range of motion in the thumb
3. More developed musculature for precise movements
4. Flatter palms and straighter fingers, facilitating tool use

These differences highlight the specialization of human hands for manipulative tasks, while other primates’ hands are often better adapted for activities like climbing and brachiating.

Hand Biomechanics: The Science of Movement

Understanding the biomechanics of the hand is crucial for fields such as ergonomics, prosthetics, and rehabilitation. How do the various components of hand anatomy work together to produce complex movements?

Hand biomechanics involves the study of:

• Joint kinematics: The motion of joints during various hand movements
• Muscle mechanics: How muscles generate force and control movement
• Tendon dynamics: The transmission of muscle force to bones
• Load distribution: How forces are distributed across the hand during different tasks

This knowledge is applied in various ways, including:

1. Designing ergonomic tools and interfaces
2. Developing more natural and functional prosthetic hands
3. Creating effective rehabilitation programs for hand injuries
4. Improving surgical techniques for hand reconstruction

The Role of Proprioception in Hand Function

Proprioception, or the sense of body position and movement, plays a crucial role in hand function. How does this sensory system contribute to our ability to use our hands effectively?

Proprioception in the hand is facilitated by specialized sensory receptors in the joints, muscles, and skin. These receptors provide constant feedback to the brain about:

• The position of fingers and joints
• The amount of force being applied
• The speed and direction of hand movements

This sensory information allows us to:

1. Perform tasks without visual feedback (e.g., typing without looking at the keyboard)
2. Adjust grip strength appropriately for different objects
3. Maintain hand stability during fine motor tasks
4. Rapidly correct errors in movement

Proprioception is essential for the smooth, coordinated movements that characterize skilled hand use.

Hand Therapy and Rehabilitation

When hand injuries or conditions occur, specialized therapy is often necessary to restore function. What approaches are used in hand therapy and rehabilitation?

Hand therapy typically involves a combination of techniques, including:

• Range of motion exercises: To maintain or improve joint flexibility
• Strengthening exercises: To rebuild muscle strength and endurance
• Sensory re-education: To improve sensation in cases of nerve injury
• Manual therapy: Hands-on techniques to mobilize joints and soft tissues
• Splinting: Custom-made devices to support healing or improve function
• Adaptive equipment training: Teaching the use of specialized tools for daily activities

The goal of hand therapy is to restore as much function as possible, allowing individuals to return to their normal activities and improve their quality of life.

Innovations in Hand Surgery and Reconstruction

Advancements in surgical techniques have dramatically improved outcomes for patients with severe hand injuries or congenital differences. What are some of the latest innovations in hand surgery and reconstruction?

Some cutting-edge approaches in hand surgery include:

1. Microsurgery: Allowing for precise repair of small blood vessels and nerves
2. Arthroscopic procedures: Minimally invasive techniques for joint repair
3. 3D-printed implants: Custom-designed prosthetics for bone and joint replacement
4. Targeted muscle reinnervation: Improving control of advanced prosthetic limbs
5. Regenerative medicine: Using stem cells and growth factors to promote healing

These innovations are expanding the possibilities for restoring hand function in even the most challenging cases, offering hope to patients who previously had limited treatment options.

The Future of Hand Research and Technology

As our understanding of hand anatomy and function continues to grow, new avenues for research and technological development are emerging. What exciting developments can we expect in the field of hand science and technology?

Some promising areas of research and development include:

• Advanced bionic hands: Prosthetics with enhanced sensory feedback and motor control
• Brain-computer interfaces: Allowing direct neural control of prosthetic hands
• Tissue engineering: Growing functional hand tissues for transplantation
• Nanotech sensors: Ultrathin electronic skin for enhanced prosthetic sensation
• Virtual reality rehabilitation: Immersive environments for hand therapy and training
• AI-assisted diagnostics: Improving the accuracy and speed of hand condition diagnosis

These advancements promise to revolutionize our ability to treat hand injuries and conditions, potentially restoring or even enhancing natural hand function.

The Impact of Hand Function on Quality of Life

The importance of hand function in our daily lives cannot be overstated. How does hand health and functionality affect overall quality of life?

Hand function impacts numerous aspects of life, including:

1. Independence in activities of daily living (e.g., dressing, eating, personal hygiene)
2. Ability to work and pursue career goals
3. Participation in hobbies and recreational activities
4. Social interactions and non-verbal communication
5. Self-esteem and body image

Recognizing the profound impact of hand function on quality of life underscores the importance of hand health, injury prevention, and effective treatment strategies. As our understanding of hand anatomy and function continues to evolve, we can look forward to even better outcomes for individuals affected by hand conditions or injuries, ultimately improving their overall well-being and life satisfaction.

Hand Anatomy Video | Medical Video Library

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 in order to learn more about diseases and conditions that can affect our hands.

Bones.

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 or MCP joint. This joint is also 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 only has 2 phalanges and one interphalangeal joint.

The first joint close to the knuckle joint is called the proximal interphalangeal joint or PIP joint. The joint closest to the end of the finger is called the distal interphalangeal joint or DIP joint.

The MCP joint and the PIP joint act like hinges when the fingers bend and straighten.

Soft tissues.

Our hand bones are held in place and supported by various soft tissues. These include: articular cartilage, ligaments, muscles and tendons.

Articular cartilage is a smooth material that acts as a shock absorber and cushions 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 tissue 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 backwards bending of the PIP joint (hyperextension).

Muscles.

Muscles are fibrous tissues that help produce movement. Muscles work by contracting.

There are two types of muscles in the hand, intrinsic and extrinsic muscles.

Intrinsic muscles are small muscles that originate in the wrist and hand. They are responsible for fine motor movement of the fingers during activities such as writing or playing the piano.

Extrinsic muscles originate in the forearm or elbow and 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.

Tendons are soft tissues that connect muscles to bones. When muscles contract, tendons pull the bones causing the finger to move. The extrinsic muscles attach 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 help in straightening the fingers, and are called extensor tendons.

Nerves.

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 are the ulnar nerve, radial nerve and median nerve. All three nerves originate at the shoulder and travel down the arm to the hand. Each of these nerves has sensory and motor components.

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.

Blood Vessels.

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.

Bursae are small fluid filled sacs that decrease friction between tendons and bone or skin. Bursae contain special cells called synovial cells that secrete a lubricating fluid.

The anatomy of the human hand is very complex. Normal hand function requires all the various bones and soft tissues that structurally form the hand to maintain proper alignment and control. Any condition or injury that disrupts this anatomy greatly impacts the function of the hand and the ability to perform activities of daily living.

Anatomy: Hand and Wrist – BID Needham

Wrist

The wrist joint is the complex joint formed between the distal ends (furthest from the body) of the Radius and Ulna (two forearm bones) and the carpal bones. It connects the forearm to the hand and allows a good range of motion. Repetitive use does however frequently lead to injuries.

Bones and Articulation

The Ulna is the larger of the two forearm bones, although it tapers at the wrist end, to become narrower than the Radius at this point. The Radius is positioned on the thumb side of the wrist, and the ulna on the little finger side. They form the wrist joint with the carpal bones. Altogether there are 8 carpal bone which are arranged in two rows, proximal and distal

• Lunate
• Triquetrum
• Pisiform
• Capitate
• Trapezium
• Trapezoid
• Hamate
• Scaphoid

The scaphoid bone crosses both rows as it is the largest carpal bone. The scaphoid and the lunate are the two bones which actually articulate with the radius and ulna to form the wrist joint.

Hand

The human hand consists of a broad palm (metacarpus) with 5 digits, attached to the forearm by a joint called the wrist (carpus).

Digits 



The four fingers on the hand are used for the outermost performance; these four digits can be folded over the palm which allows the grasping of objects. Each finger, starting with the one closest to the thumb, has a colloquial name to distinguish it from the others

• Index finger, pointer finger, or forefinger
• Middle finger
• Ring finger
• Little finger or ‘pinky’
• Thumb

Bones

The human hand has 27 bones: the carpals or wrist accounts for 8; the metacarpals or palm contains five; the remaining fourteen are digital bones; fingers and thumb.

The palm has five bones known as metacarpal bones, one to each of the 5 digits. These metacarpals have a head, a shaft, and a base.

Human hands contain fourteen digital bones, also called phalanges, or phalanx bones: two in the thumb (the thumb has no middle phalanx) and three in each of the four fingers. These are the distal phalanx, carrying the nail, the middle phalanx, and the proximal phalanx.

Sesamoid bones are small ossified nodes embedded in the tendons to provide extra leverage and reduce pressure on the underlying tissue. Many exist around the palm at the bases of the digits; the exact number varies between different people.

Articulation

The articulation of the human hand is more complex and delicate than that of comparable organs in any other animal. Without this extra articulation, we would not be able to operate a wide variety of tools and devices, nor achieve the wide variety of possible hand gestures.

The articulations are

• Interphalangeal articulations of hand (the hinge joints between the finger bones)
• Metacarpophalangeal joints (where the fingers meet the palm)
• Intercarpal articulations (where the palm meets the wrist)
• Wrist (may also be viewed as belonging to the forearm)

Most Common Hand/Wrist Injuries

While hand and wrist injuries are very common, some athletes never seek treatment. Unfortunately, delaying the diagnosis and treatment may result in long-term problems or even a permanent disability. Here is a list of some of the most common injuries athletes experience.

Hand tendon injury, wrist joint treatment in Germany

One of the activities of Medical Connections is shoulder and hand surgery. The medical center where the operations take place is the base of the Olympic Center in Bavaria, and one of the few in Germany that has a FIFA certificate. The doctor operates on more than 1300 patients a year, most of them are served on an outpatient basis. Most of our patients are professional athletes, as well as people who just go in for sports. We actively cooperate with professional sports clubs. In particular, we work with the Moscow football club CSKA, we often host athletes from St. Petersburg.

The hand is a complex and multifunctional organ. With the help of hands, we eat, dress, work at a computer, drive a car, create works of art, play sports. The complex movements that the human hand can perform are possible due to the structure of the hand.

• Hand injury

• Tendon of the hand

Hand structure

The human skeleton consists of 207 bones, 27 of which are in the hand and wrist.

In the human hand there are 29 large joints, 123 ligaments and 34 muscles with which the fingers move. The fingertips contain some of the densest areas of nerve endings on the body.

Wrist injuries

It is not surprising that with so many bones, joints, ligaments and muscles, the wrist joint is damaged very easily, and its injuries are among the most common among athletes. It is worth noting that with proper treatment, you can count on a complete restoration of sports form.

The most common injuries of the hand and wrist joint in athletes

There are two types of injuries that athletes can experience. The first includes traumatic (acute), the second – reloading (chronic) injuries. Traumatic injuries are most common among athletes involved in contact sports such as football, hockey or wrestling. Common traumatic injuries are dislocations, sprains, partial muscle injuries, bone fractures, tendon inflammation and ligament ruptures. with regard to fractures, fractures of the bones of the fingers most often occur.

Overload conditions are more typical for sports where the athlete must repeatedly repeat the same movements. These are tennis, baseball, golf and others.

Overload injuries are caused by increased stress on certain structures and include inflammation in the tendons, tendon dislocations, nerve damage and stress fractures of the bones, also arising from repetitive and prolonged loads.

Most often, the recovery period is longer after acute injuries. If left untreated, chronic problems can also have a significant impact on limb function and athletic performance.

What to do if a hand or wrist injury occurs

If you have been injured in a hand or wrist joint at competitions where there is no doctor, then you should definitely go to the clinic if you have the following symptoms:

• severe pain;
• pronounced edema;
• numbness;
• finger or hand becomes dark, grey, cold;
• there is a clear deformity of the fingers or wrist joint;
• there are clicks, a feeling of displacement of tissues and bones during movements;
• bleeding that does not decrease and lasts more than 15 minutes.

If, after a minor injury, pain and swelling persist for two weeks, you should contact your general practitioner or local physician, who will examine you and, if necessary, refer you to a specialist.

For minimal trauma and injury, the simplest home treatment, which should include rest, compression, elevation, and cold, usually helps. Non-steroidal anti-inflammatory drugs, which your doctor can also prescribe, may also be helpful.

What treatments are available for hand and wrist injuries

The methods of treatment of the wrist joint in Germany depend on the location of the injury, the type and severity of the injury. in some cases, surgical treatment is required, for example, for torn ligaments, although very often medication, immobilization, or physical therapy procedures are sufficient. The doctor will choose the most appropriate method, taking into account short-term and long-term prognosis, possible deformities and function.

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Handanatom – anatomy of the hand

If we consider the hand as a whole, then, as in any other department of the human musculoskeletal system, three main structures can be distinguished in it: the bones of the hand; ligaments of the hand that hold bones and form joints; hand muscles.

Hand bones
The hand has three sections: the wrist, metacarpus and fingers.

Carpal bones
The eight small carpal bones are irregularly shaped. They are located in two rows.

The proximal row consists of the following bones, if you go from the side of the thumb to the side of the fifth finger: scaphoid, lunate, trihedral and pisiform.

The distal row is also made up of four bones: polygonal, trapezoid, capitate and hook-shaped, which with its hook faces the palmar side of the hand.

The proximal row of carpal bones forms an articular surface convex towards the radius. The distal row is connected to the proximal row with an irregularly shaped joint.

The bones of the wrist lie in different planes and form a groove (carpal groove) on the palmar surface and a bulge on the back. The tendons of the flexor muscles of the fingers run in the groove of the wrist. Its inner edge is limited by the pisiform bone and hook of the hamate bone, which are easily palpable; the outer edge is composed of two bones – the scaphoid and the polygonal.

Metacarpus bones
The metacarpus consists of five tubular metacarpal bones. The metacarpal bone of the first finger is shorter than the others, but differs in its massiveness. The longest is the second metacarpal bone. The following bones decrease in length towards the ulnar edge of the hand. Each metacarpal has a base, body, and head.

The bases of the metacarpal bones articulate with the carpal bones. The bases of the first and fifth metacarpal bones have saddle-shaped articular surfaces, and the rest have flat articular surfaces. The heads of the metacarpal bones have a hemispherical articular surface and articulate with the proximal phalanges of the fingers.

Finger bones
Each finger consists of three phalanges: proximal, middle and distal. The exception is the first finger, which has only two phalanges – proximal and distal. The proximal phalanges are the longest, the distal phalanges are the shortest. Each phalanx has a middle part – the body and two ends – proximal and distal. At the proximal end is the base of the phalanx, and at the distal end is the head of the phalanx. At each end of the phalanx there are articular surfaces for articulation with adjacent bones.

Sesamoid bones of the hand
In addition to these bones, the hand also has sesamoid bones, which are located in the thickness of the tendons between the metacarpal bone of the thumb and its proximal phalanx. There are also inconstant sesamoid bones between the metacarpal bone and the proximal phalanx of the second and fifth fingers. Sesamoid bones are usually located on the palmar surface, but occasionally they are also found on the dorsal surface. The pisiform bone is also referred to as a sesamoid bone. All sesamoid bones, as well as all bone processes, increase the leverage of the muscles that attach to them.

Ligaments of the hand

Wrist joint
The radius and bones of the proximal row of the wrist take part in the formation of this joint: the scaphoid, lunate and trihedral. The ulna does not reach the surface of the radiocarpal joint (it is “complemented” by the articular disc). Thus, in the formation of the elbow joint, the ulna plays the largest role of the two bones of the forearm, and the radius plays the largest role in the formation of the radiocarpal joint.

In the radiocarpal joint, which has an elliptical shape, flexion and extension, adduction and abduction of the hand are possible. Pronation and supination of the hand occurs along with the same movements of the bones of the forearm. A small passive movement of a rotational nature is also possible in the radiocarpal joint (by 10-12°), but it occurs due to the elasticity of the articular cartilage. The position of the fissure of the radiocarpal joint is determined from the back surface, where it is easily detected through soft tissues; in addition, its position is determined from the radial and ulnar sides. On the radial side, in the region of the inferior radial fossa, one can feel the gap between the lateral styloid process and the navicular bone. On the ulnar side, a recess is palpated between the head of the ulna and the triquetral bone, corresponding to the ulnar portion of the cavity of the radiocarpal joint.

Movements in the radiocarpal joint are closely related to movements in the midcarpal joint, which is located between the proximal and distal rows of carpal bones. This joint has a complex surface of irregular shape. The total amount of mobility during flexion of the hand reaches 85°, and during extension it is also approximately 85°. Adduction of the hand in these joints is possible by 40°, and abduction by 20°. In addition, a circular motion (circumduction) is possible in the radiocarpal joint.

The radiocarpal and midcarpal joints are reinforced with numerous ligaments. The ligamentous apparatus of the hand is very complex. Ligaments are located on the palmar, dorsal, medial and lateral surfaces of the wrist, as well as between the individual bones of the wrist. The most important are the collateral ligaments of the wrist – the radius and the ulna. The first goes from the lateral styloid process to the navicular bone, the second – from the medial styloid process – the trihedral bone.

Between the bone elevations on the radial and ulnar sides of the palmar surface of the hand, a ligament is thrown – the flexor retinaculum. It is not directly related to the joints of the hand, but is, in fact, a thickening of the fascia. Throwing over the groove of the wrist, it turns it into a carpal tunnel, where the tendons of the flexors of the fingers and the median nerve pass.

Carpometacarpal joints of the hand
They are connections of the distal row of carpal bones with the bases of the metacarpal bones. These joints, with the exception of the carpometacarpal joint of the thumb, are flat and inactive. The range of motion in them does not exceed 5-10°. Mobility in these joints, as well as between the bones of the wrist, is sharply limited by well-developed ligaments.

The ligaments located on the palmar surface of the hand make up a strong palmar ligamentous apparatus. It connects the bones of the wrist to each other, as well as to the metacarpal bones. On the hand, ligaments can be distinguished that run arcuately, radially and transversely. The central bone of the ligamentous apparatus is the capitate, to which a greater number of ligaments are attached than to any other bone of the wrist. The dorsal ligaments of the hand are much less developed than the palmar ligaments. They connect the bones of the wrist to each other, making up the thickening of the capsules that cover the joints between these bones. The second row of carpal bones, in addition to the palmar and dorsal ligaments, also has interosseous ligaments.

Due to the fact that the bones of the distal row of the wrist and the four (II-V) bones of the metacarpus are inactive relative to each other and are firmly connected into a single formation that makes up the central bone nucleus of the hand, they are designated as the solid base of the hand.

The carpometacarpal joint of the thumb is formed by the polygonal bone and the base of the first metacarpal bone. The articular surfaces are saddle-shaped. The following movements are possible in the joint: adduction and abduction, opposition (opposition) and reverse movement (reposition), as well as circular movement (circumduction). Due to the opposition of the thumb to all other fingers, the volume of grasping movements of the hand increases significantly. The amount of mobility in the carpometacarpal joint of the thumb is 45-60° in abduction and adduction and 35-40° in opposition and reverse movement.

Metacarpophalangeal joints of the hand
Formed by the heads of the metacarpal bones and the bases of the proximal phalanges of the fingers. All these joints have a spherical shape and, accordingly, three mutually perpendicular axes of rotation, around which flexion and extension, adduction and abduction, as well as circular motion (circumduction) occur. Flexion and extension are possible at 90-100°, abduction and adduction – at 45-50°.

The metacarpophalangeal joints are strengthened by collateral ligaments located on the sides of them. On the palmar side, the capsules of these joints have additional ligaments called palmar. Their fibers are intertwined with the fibers of the deep transverse metacarpal ligament, which prevents the heads of the metacarpal bones from moving apart.

Interphalangeal joints of the hand
They have a block-like shape, their axes of rotation pass transversely. Flexion and extension are possible around these axes. Their volume in the proximal interphalangeal joints is 110-120°, while in the distal – 80-90°. All interphalangeal joints are strengthened by well-defined collateral ligaments.

Fibrous and synovial sheaths of the tendons of the fingers of the hand

Ligaments of the flexor retinaculum and extensor retinaculum are of great importance for strengthening the position of the muscle tendons passing under them, especially during flexion and extension of the hand: the tendons rest on the named ligaments from their inner surface, and connect prevent the tendons from moving away from the bones and, with a strong contraction of the muscles, withstand significant pressure.

The sliding of the tendons of the muscles passing from the forearm to the hand and the reduction of friction are facilitated by special tendon sheaths, which are fibrous or bone-fibrous channels, inside of which there are synovial sheaths, in some places extending beyond these channels. The largest number of synovial sheaths (6-7) is located under the extensor retinaculum. The formation of the channels involves the ulna and radius, which have grooves corresponding to the places where the tendons of the muscles pass, and fibrous bridges that separate one channel from the other, which go from the extensor retinaculum to the bones.

The palmar synovial sheaths belong to the tendons of the flexors of the hand and fingers that run in the carpal tunnel. The tendons of the superficial and deep flexors of the fingers lie in a common synovial sheath, which extends to the middle of the palm, reaching the distal phalanx of only the fifth finger, and the tendon of the long flexor of the thumb is in a separate synovial sheath, which passes along with the tendon to the finger. In the area of ​​the palm, the tendons of the muscles that go to the second, third and fourth fingers are deprived of synovial sheaths at some distance and receive them again on the fingers. Only the tendons leading to the fifth finger have a synovial sheath, which is a continuation of the common synovial sheath for the flexor tendons of the fingers.

Muscles of the hand

On the hand, the muscles are located only on the palmar side. Here they form three groups: middle (in the middle section of the palmar surface), a group of muscles of the thumb and a group of muscles of the thumb. A large number of short muscles on the hand is due to the fine differentiation of finger movements.

Middle hand muscle group
Consists of worm-like muscles that start from the tendons of the deep flexor of the fingers and are attached to the base of the proximal phalanges of the second to fifth fingers; palmar and dorsal interosseous muscles, which are located in the interosseous spaces between the metacarpal bones and are attached to the base of the proximal phalanges of the second to fifth fingers. The function of the muscles of the middle group is that they are involved in the flexion of the proximal phalanges of these fingers. In addition, the palmar interosseous muscles bring the fingers of the hand to the middle finger, and the dorsal interosseous muscles spread them apart.

Thumb muscle group
Forms the so-called elevation of the thumb on the hand. They start on the nearby bones of the wrist and metacarpus. Among them, there are: a short muscle that removes the thumb, which is attached to its proximal phalanx; a short flexor of the thumb, attached to the external sesamoid bone, located at the base of the proximal phalanx of the thumb; muscle that opposes the thumb, going to the first metacarpal bone; and the adductor thumb muscle, which inserts on the internal sesamoid bone located at the base of the proximal phalanx of the thumb. The function of these muscles is indicated in the name of each muscle.

Thumb muscle group
Forms an elevation on the inside of the palm. This group includes: a short palmar muscle; muscle that removes the little finger; the short flexor of the little finger and the muscle that opposes the little finger. They originate from nearby carpal bones and insert at the base of the proximal phalanx of the fifth toe and fifth metacarpal.