How many knuckles in a finger: Illustration Picture of Hand Structures – Finger Anatomy

Normal Hand Anatomy Colorado | Hand and Wrist Bones Lone Tree

Home » Patient Info » Conditions & Procedures » Hand & Wrist » Normal Hand Anatomy

The hand in the human body is made up of the wrist, palm, and fingers. The most flexible part of the human skeleton, the hand enables us to perform many of our daily activities. When our hand and wrist are not functioning properly, daily activities such as driving a car, bathing, and cooking can become impossible.

The hand’s complex anatomy consists of 27 bones, 27 joints, 34 muscles, over 100 ligaments and tendons, numerous blood vessels, nerves, and soft tissue.

It is important to understand the normal anatomy of the hand in order to learn about diseases and conditions that can affect our hands.

Skeletal Anatomy

The wrist is comprised of 8 bones called carpal bones. These wrist bones connect to 5 metacarpal bones that form the palm of the hand. Each metacarpal bone connects to one finger or a thumb at a joint called the metacarpophalangeal joint, or 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 joints. The first joint, closest to the knuckle joint, is the proximal interphalangeal joint or PIP joint. The second joint nearer the end of the finger is called the distal interphalangeal joint, or DIP joint. The thumb in the human body only has 2 phalanges and one interphalangeal joint.

Soft Tissue Anatomy

Our hand and wrist bones are held in place and supported by various soft tissues. These include

  • Cartilage: Shiny and smooth, cartilage allows smooth movement where two bones come in contact with each other.

  • Tendons: Tendons are soft tissue that connects muscles to bones to provide support. Extensor tendons enable each finger to straighten.

  • Ligaments: Ligaments are strong rope like tissue that connects bones to other bones and help hold tendons in place providing stability to the joints. The volar plate is the strongest ligament in the hand and prevents hyperextension of the PIP joint.

  • Muscles: Muscles are the fibrous tissues capable of contracting to cause body movement.

Interestingly, the fingers contain no muscles. Small muscles originating from the carpal bones of the wrist are connected to the finger bones with tendons. These muscles are responsible for movement of the thumb and little finger enabling the hand to hold and grip items by allowing the thumb to move across the palm, a movement referred to as thumb opposition. The smallest muscles of the wrist and hand are responsible for fine motor movement of the fingers.

  • Nerves: Nerves are responsible for carrying signals back and forth from the brain to muscles in our body, enabling movement and sensation such as touch, pain, and hot or cold. The three main nerves responsible for hand and wrist movement all originate at the shoulder area and include the following

Radial: 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 third finger.

Median: The median nerve travels through the wrist tunnel, also called carpal tunnel, providing sensation to the thumb, index finger, long finger, and part of the ring finger.

Ulnar: The ulnar nerve travels through a tunnel in the wrist called Guyon’s tunnel formed by two carpal bones and the ligament that connects them together. The ulnar nerve supplies feeling to the little finger and half of the ring finger.

  • Blood Vessels: The two main vessels of the hand and wrist are

Radial Artery: The radial artery is the largest artery supplying the hand and wrist area. Traveling across the front of the wrist, nearest the thumb, it is this artery that is palpated when a pulse is counted at the wrist.

Ulnar Artery: he ulnar artery travels next to the ulnar nerve through Guyon’s canal in the wrist. It supplies blood flow to the front 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. When this fluid becomes infected, a common painful condition known as bursitis can develop.

Normal Movement

Biomechanics is a term to describe movement of the body. The fingers of the hand permit the following movements at the metacarpophalangeal joint (MCP) or knuckle joint.

Flexion: Moving the base of the finger towards the palm.

Extension: Moving the base of the fingers away from the palm.

Adduction: Moving the fingers toward the middle finger.

Abduction: Moving the fingers away from the middle finger.

Flexion: Moving the last two segments of the finger towards the base of the fingers.

Extension: Moving the last two segments of the finger away from the base of the fingers.

Biomechanics of the wrist include the following:

Flexion: Moving the palm of the hand towards the front of the forearm.

Extension: Moving the back of the hand towards the back of the forearm.

Adduction: Moving the pinky side of the hand toward the outer aspect of the forearm.

Abduction: Moving the thumb side of the hand toward the inner aspect of the forearm.

The thumb performs different movements at three separate joints. The carpometacarpal joint is where the wrist bones, carpals, meet the metacarpals, the bones in the palm of the hand. At this articulation, the following movements can be performed

Abduction: Moving the bone below the thumb towards the palm of the hand.

Extension: Moving the bone below the thumb away from the hand.

Adduction: Moving the bone below the thumb towards the back of the wrist.

Abduction: Moving the bone below the thumb towards the front of the wrist.

Opposition: Moving the thumb across the palm of the hand touching the other fingers.

The following movements occur at the metacarpophalangeal joint or MCP joint at the base of the thumb

Flexion: Moving the joint at the base of the thumb towards the heel of the hand.

Extension: Moving the joint at the base of the thumb away from the heel of the hand.

Adduction: Movement of the thumb base towards the back of the hand.

Abduction: Movement of the thumb base away from the back of the hand.

At the interphalangeal joint of the thumb or IP joint, the following movements can be performed:

Flexion: Bending the top of the thumb towards the base of the thumb.

Extension Hyperextension: Moving the top of the thumb away from the base of the thumb.

  • Trigger Finger

  • Dupuytren’s Contracture

  • De Quervain’s Tenosynovitis

  • Carpal Tunnel Syndrome

  • Wrist Fracture

  • Arthroscopic Wrist Surgery

  • Wrist Joint Replacement

How do hands work? – InformedHealth.


Created: August 31, 2010; Last Update: July 26, 2018; Next update: 2021.

Hands have a very delicate and complex structure. This gives muscles and joints in the hand a great range of movement and precision. The different forces are also distributed in the best possible way. Thanks to this structure, you can do a wide range of things with your hands, such as grip objects tightly and lift heavy weights, as well as guide a fine thread through the tiny eye of a needle.

Hands are also quite vulnerable, though: Tendons, nerve fibers, blood vessels and fairly thin bones are all positioned right under the skin and are only protected by a thin layer of muscle and fat. Only the palm is protected by a strong pad of tendons (aponeurosis), enabling a powerful grip. Our hands are put through quite a lot every day, and often come into contact with potentially harmful objects. As a result, hand injuries and problems due to wear and tear are very common.

The right and left hand are each controlled by the opposite side of the brain. Usually one hand is preferred for carrying out fine and complex movements, so we often say people are either right- or left-handed.

Bones and joints

The human hand is made up of a total of 27 individual bones: 8 carpal bones, 5 metacarpal bones and 14 “finger bones” (also called phalanges) are connected by joints and ligaments. About one quarter of all our body’s bones are found in our hands. The hand can be divided up into three different areas based on the joints:

The human hand has a total of 27 individual bones in it


The wrist is made up of two parts of a joint that work as one functional unit. It allows us to flex (bend) or extend (stretch) our hands. We can also tilt our hands sideways, towards our little finger or thumb.


The eight carpal bones are held together tightly by ligaments, and are more or less fixed in place. They are positioned in two rows of four carpal bones each. Together with the radius bone in the forearm, two of the carpal bones (the scaphoid bone and the lunate bone) form the lower part of the wrist joint, which is very important for hand movements. The ulna bone in the forearm is separated from the carpal bones by a cartilage disc. The other part of the joint is located between the two rows of carpal bones.


After the second row of carpal bones comes the metacarpus. This middle part of the hand consists of five long metacarpal bones. You can feel them quite clearly on the back of your hand. One of the carpal bones and the long thumb bone come together to form the basal joint of the thumb. Known as the carpometacarpal joint, it enables the thumb to be particularly flexible.


The freely movable part of our hand is made up of five digits (four fingers and one thumb). Each finger has three individual bones, and the thumb only has two. The fingers have three joints each, which can only be bent and stretched in one direction. The thumb is the only digit that can twist, thanks to the saddle-shaped carpometacarpal joint.


There are over 30 muscles in the hand, working together in a highly complex way. Movements of the hand are mostly started by muscles in the forearm. Only the thin tendons of these muscles are found directly in the hand: the extensor tendons used for stretching the hand run through the back of the hand to the tips of the fingers, and the flexor (bending) tendons run through the palms to the fingers.

Short muscles of the hand

There are short muscles between the individual metacarpal bones of the hand. They allow us to spread our fingers (abduction) and then pull them back together (adduction). They also help to bend and stretch the fingers.

The thenar eminence and the hypothenar eminence muscles

Two groups of more powerful muscles in the hand itself make up the thenar eminence (at the base of the thumb) and the hypothenar eminence (controlling the movement of the little finger). Among other things, the thenar muscles enable the thumb and the tips of the four fingers to touch each other (opposable thumb). A separate muscle (the adductor pollicis) is used to pull the thumb towards the palm. The hypothenar eminence muscles are mainly used for mainly used for sticking out the little finger and pulling it inwards again, and for tightening the skin that covers the hypothenar eminence.


The lumbricals of the hand are four thin, worm-like muscles that help bend the metacarpophalangeal joints and extend the fingers.

Connective tissue and tendons

Some parts of the long flexor and extensor tendons of the forearm muscles are surrounded by protective layers called tendon sheaths. Tendon sheaths contain a fluid that acts as a lubricant. This allows the tendons to slide smoothly through the sheaths, without friction.

Muscle tendons, nerves and blood vessels running from the forearm to the hand pass through a tunnel-like passageway on the palm side of the wrist. Known as the carpal tunnel, this passageway is made up of strong connective tissue and carpal bones. 

The carpal tunnel (seen from the palm side of the hand)

Function of the muscles: Power, touch and precision

Our hands can grasp and move objects in two different ways: with a power grip or precision grip. The object’s size, shape, weight and ease of handling determines which of these two approaches is used. The power grip is better suited for large, heavy objects, and the precision grip is used for small, delicate objects.

Power grip

The power grip is used to do things like carry heavy bags or hold on to a handle. In the power grip, the object is held in the palm of the hand, and the long flexor tendons pull the fingers and the thumb so that they can tightly grasp the object. This grip is made possible by the four other fingers flexing (bending) and, most importantly, the ability of the thumb to be positioned opposite the fingers. With the hand in this position, larger objects such as a stone or a heavy bottle can be held and moved in a controlled way. The heavier the weight and the smoother the surface is, the more strength is needed to hold and move the object.

Precision grip

The precision grip is important for moving small and delicate objects, for example when writing, sewing or drawing. When using the precision grip, the thumb and the index (“pointer”) finger work like tweezers: The thumb is opposite one or more fingertips, allowing the hand to grip even very small objects – like pencils or delicate instruments – in a controlled way.

Blood supply

The hand is supplied with blood through two main arteries: one on the same side as the thumb, and one on the same side as the little finger. These two arteries each curve around in an arch shape where the palm is, so that the hand is supplied with oxygen-rich blood through a double loop. These loops have branches leading off into the individual fingers. Each artery is accompanied by veins and nerves: In total, each finger is supplied by four bundles of nerves and blood vessels. 

Location of the main nerves and blood vessels in the hand


The muscles and skin of the hand are supplied by three nerves:

  • the radial nerve (nervus radialis),

  • the median nerve (nervus medianus), and

  • the ulnar nerve (nervus ulnaris).

The ulnar nerve moves the muscles of the hypothenar eminence, the muscles between the bones of the metacarpus, the muscle that pulls the thumb inwards (adductor pollicis) and two of the lumbrical muscles between fingers. This nerve also picks up sensations from the area below the little finger and the side of the ring finger closest to it.

The median nerve is responsible for the movement of the thenar eminence muscles and the rest of the lumbricals. It is also responsible for the perception of skin sensations on the palm, thumb, index finger, and middle finger, as well as sensations on the side of the ring finger closest to the middle finger.

The radial nerve activates the finger extensors and the muscles in the wrist that are responsible for extending the hand. It also carries sensations from the skin on the back of the hand and the back of the thumb to the brain.

The sense of touch

The fingers on one hand are bent and stretched about 25 million times over the course of a lifetime. Our hands also have very sensitive “antennae” for receiving information from the environment: There are a total of 17,000 touch receptors and free nerve endings in the palm. These pick up sensations of pressure, movement and vibration, so it is with good reason that the sense of touch is often associated with the hand. The skin on our fingertips is especially sensitive to touch. 


  • Lippert H. Lehrbuch Anatomie. München: Urban und Fischer; 2003.

  • Menche N (Ed). Biologie Anatomie Physiologie. München: Urban und Fischer; 2012.

  • Pschyrembel. Klinisches Wörterbuch. Berlin: De Gruyter; 2017.

  • Schmidt R, Lang F, Heckmann M. Physiologie des Menschen: mit Pathophysiologie. Berlin: Springer; 2011.

  • IQWiG health information is written with the aim of helping
    people understand the advantages and disadvantages of the main treatment options and health
    care services.

    Because IQWiG is a German institute, some of the information provided here is specific to the
    German health care system. The suitability of any of the described options in an individual
    case can be determined by talking to a doctor. We do not offer individual consultations.

    Our information is based on the results of good-quality studies. It is written by a
    team of
    health care professionals, scientists and editors, and reviewed by external experts. You can
    find a detailed description of how our health information is produced and updated in
    our methods.

The myth of people whose joints bend to both sides

  • Jason G. Goldman
  • BBC Future

Sign up for our ”Context” newsletter : she will help you understand the events.

Image copyright Thinkstock

There are no people in nature whose joints actually bend to either side, although some of us do have very flexible joints. And this property can lead to very unexpected effects, says the correspondent
BBC Future .

Surely you know someone (or, more likely, you knew in childhood) who boasted that his joints flexed in both directions. As proof, these braggarts would bend their thumb backwards so that it could touch their wrist. However, for all their boasting, these schoolyard performance artists are not actually medical phenomena. At the very least, humans can’t have joints that flex to either side. But what about these bouncers, whose bodies and limbs are able to wobble in the most incredible way, as if on hinges? They are simply incredibly flexible.

Doctors and scientists call this hypermobility or elasticity of the joints. It just means that some people can bend their joints more than others. Most of us can flex our thumb a few degrees, but some can flex it at a large angle. We can all bend at the waist, but for some individuals, their lumbosacral joints allow them to lean back and place both hands on the floor. Each of us can spread our legs wide, but only some of the hip joint is so mobile that it allows them to sit on the splits.

(Similar articles in the “Journal” section)

And in order to be able to talk about joint hypermobility, such flexibility must be innate, and not acquired as a result of training or stretching. Some athletes and dancers, for example, can eventually train their bodies to become more and more flexible, but the hyper-mobility of the joints that preoccupies us right now is an innate property.

A brief lesson in human anatomy is required to understand what makes a joint more or less flexible. There are two factors that limit joint mobility: the shape of the bones and cartilage, or ligaments. Mykal Habib, an anatomist and vertebrate palaeontologist at the University of Southern California, says: “You can have a hard time exercising – it can be because something is pushing against something – or you can have a ligament, that will keep everything in its place.”

Hooks and slots

If a person can bend his thumb to the wrist, it is usually because his ligaments allow him to do so. “If you have weakened ligaments from birth, then they will be more mobile,” says Habib.

On the other hand, some of those individuals whose joints seem to bend in both directions owe their flexibility to the structure of their own bones. A typical case of hypermobility refers to the joints of the elbows. Some people are able to bend their elbow joint in the “wrong” direction so that an angle exceeds 180 degrees.

Image Credit: Getty

Skip the Podcast and continue reading.


What was that?

We quickly, simply and clearly explain what happened, why it’s important and what’s next.


End of Story Podcast

There is a bone that forms the sharp part of the shoulder called the olecranon or olecranon. “He has a small hook, although in fact this hook is quite large,” Khabib explains. This hook is located in a small groove located on the back of the humerus; this is the upper arm bone – the humerus or humerus. And when you straighten your arm, the hook slides and falls into this little groove. When the hook hits the end of the groove, you can’t bend your arm any further.

“If your olecranon is small or if the groove is deep, then you will be able to extend your arm more than 180 degrees,” Habib says. bones have a slightly different structure.

In 2004, a study was conducted in the UK on adult female twins. It was supposed to confirm the earlier assumptions that joint hypermobility is genetically determined. It turned out that in pairs of identical twins, both sisters more often had joint hypermobility than in pairs of fraternal twins. Back at 19In the 1930s and 1940s, researchers found that joint hypermobility usually runs in families.

Researchers have also found that joint hypermobility decreases with age. Children tend to be more flexible than their parents and grandparents. In women, joints tend to be more flexible than in men, although this may be due to the fact that men are usually larger. There is also evidence that people of African, Asian, and Middle Eastern ancestry are generally more hypermobile than European descendants.

Most super-flexible people are not harmed by these qualities. However, some can be diagnosed with one of the symptoms of the so-called Ehlers-Danlos syndrome, which can be very painful. Dr. Michael Simpson wrote in an article published in the Journal of the American Osteopathic Association that 4 to 13% of people have symptoms of Ehlers-Danlos syndrome, usually in the thumbs, little fingers, elbows, knees, and spine.

Dancer’s dilemma

There is a group of people with joint hypermobility that most often becomes the object of scientific research – dancers. Joint hypermobility, even in its mildest form, is often associated with a lack of stability. “If a joint is really flexible, it won’t be stable enough and you end up using more muscle strength to keep it in place,” Habib says.

Image copyright Getty

Image caption,

Women are said to have more flexible joints than men

Because of this, people with increased joint mobility end up having to use their energy to maintain balance instead of doing the things they want – for example, lifting weights (in the case of the elbows) or even just standing up straight (in the case of the knees and back).

In a report published in 2012, physiotherapist Mark Scheper of the Amsterdam University of Applied Sciences explicitly questioned whether hypermobility is “a sign of talent or vulnerability” for professional dancers. “From an aesthetic point of view, hypermobility of the joints is often presented – and indeed looks – as part of a professional dance education,” he writes, but this can lead to such dancers being more prone to pain and fatigue than their counterparts with less flexible joints. As a result, the dancer may develop psychological symptoms of depression and anxiety.

For their research, Scheper and colleagues recruited dancers from the Amsterdam School of the Art Academy and compared them with girls from the nearby Amsterdam Medical School. The scientist found that, in general, joint hypermobility is usually accompanied by “less muscle strength, reduced maximum exercise capacity, and less ability to walk distances.” This pattern was observed in patients from both schools. However, joint hypermobility was much more common in dancers than in medical women.

Strength Test

Dancers with joint hypermobility were more likely to complain of severe fatigue than medical school students with the same symptoms. The researchers suspect that this may reflect the fact that dance education generally requires more activity, but it also suggests that even with all their training, dancers are less physically fit than medical school girls. In addition, dancing at a professional level requires not only flexibility, but also greater control and high precision of movements. Thus, those with more flexible joints may be more fatigued while achieving precise movements.

Image copyright, Getty

Image caption,

Those with more flexible joints may be more fatigued to achieve precise movements

All dancers were more tired than medical dancers, but dancers with hyperactive joints were the most tired. “Perhaps,” Scheper writes, “such dancers have to put in more effort to meet the requirements of professional dance education, but they also have to put in more effort to maintain their skills.”

In light of their research, Scheeper and colleagues suggested that joint hypermobility may be more of a disadvantage than an advantage for professional dancers.

However, we should avoid generalizations, say British rheumatologists Howard Byrd and Elaine Foley. With advanced knowledge and understanding of anatomy, Byrd and Foley point out that the art of dance is not something monolithic.

“The requirements for ballet dancers are different from those for contemporary dancers,” they write. After all, even if we talk only about modern dance, the styles and techniques of outstanding choreographers, such as the late Martha Graham and Merce Cunningham, are strikingly different from each other.

Indeed, evaluating the effect of superflexibility on dance requires more research than the modest study of joints.

the original of this article in English is available on the website
BBC Future .

Trigger finger (Knott’s disease, stenosing ligamentitis)

Causes of finger snapping

Symptoms of Knott’s disease

Pathogenesis of stenosing ligamentitis

Treatment of Knott’s disease

Trigger finger (Knott’s disease, stenosing ligamentitis) is characterized by the inability to independently straighten the finger from the flexion position.

Causes of finger snapping

In most cases, the disease develops gradually. The most common cause of stenosing ligamentitis is trauma to the annular ligament, which is located under the transverse fold of the hand. This is mainly due to the wearing of weights, pull-ups on the horizontal bar, blows to the palmar surface of the hand. Also, finger snapping can occur against the background of chronic monotonous movements (working on the keyboard, assembling parts, sorting something).

Symptoms of Knott’s disease

Most often, there is a complaint of soreness of the palmar surface of the hand, respectively, the metacarpophalangeal joint, when flexing and extending the finger and when pressing on this place with the handle of a tool, lever, suitcase, etc. Often, pain radiates to the finger, or closer to the wrist – along the palmar surface. The finger hurts during work, but often the pain bothers at rest and, in particular, at night.

Usually painful restriction of movement, accompanied by clicking, most noticeable in the morning, after a long time without movement. Night pains, accompanied by irradiation, sometimes cause debilitating insomnia. Many patients, even without consulting a doctor, understand that in the morning you need to warm your hands in warm-hot water, rub your palm, do gymnastics for your finger, after which clicks become less painful, and finger movements become freer (when the hand “developed”).

Pathogenesis of stenosing ligamentitis

As a result of trauma, inflammation of the annular ligament occurs, turning into its swelling, thickening. The flexor tendon, which passes under it, continues to move (the person is engaged in daily activities, work). The friction between the ligament and tendon sheaths increases, as a result of which they swell, and a club-shaped thickening of the tendon occurs. The knot with some resistance passes the annular ligament, injuring it even more.

Vicious circle. The finger is now “trapped” in a flexed position, and the patient is often unable to straighten it on his own, as there is not enough extensor force to allow the thickened portion of the tendon to overcome the narrowing of the annular ligament. And if this happens, then with a click. In order to remove the snapped finger from a fixed position, patients begin to help with the second – healthy – hand.

Over time, flexion and extension begin to be accompanied not only by a click, but also by pain. This suggests that the changes are already irreversible, and conservative treatment will most likely be unsuccessful.

Treatment of Knott’s disease

In the early stages of the disease, conservative therapy is possible. It includes functional rest (do not actively load the hand, fingers), physiotherapy, a course of non-steroidal anti-inflammatory drugs (topically and orally).

If this therapy is ineffective, local injections with steroidal anti-inflammatory drugs can be performed. They permanently reduce signs of inflammation, pain and swelling. The drug is injected into the area around the ligament or tendon.

If conservative treatment fails, surgery is indicated (dissection of the annular ligament). Surgery is a very effective treatment for trigger finger, as it leaves no restrictions on the movement of the tendon in the canal. This small outpatient surgery can be performed under local anesthesia. During the operation, a small skin incision is made on the palmar surface of the hand in the projection of the distal palmar fold, and the ligament is dissected.

Full range of motion is restored immediately after surgery. The wound heals within 10-12 days, after which the stitches are removed. Already in the early postoperative period, you need to start developing finger movements.

In this way, Knott’s disease, which the patient has suffered for a long time, can be cured very quickly, once and for all.

The author of the article:

Starochkin Konstantin Anatolyevich

traumatologist-orthopedist, surgeon

work experience 18 years

reviews leave a review


m. Sukharevskaya



  • Title
  • Consultation of a traumatologist-orthopedist based on the results of studies in third-party medical organizations2700