Hand: Bones and joints of the hand

The hand combines precision and strength: it must grasp objects, perform fine finger movements, and support the weight of the palm. This is achieved not by a single "large" bone, but by a system of many smaller bones connected by joints and held together by ligaments and tendons. [1]

The hand skeleton is usually described as having three levels: the wrist, the metacarpus, and the phalanges. This totals to eight carpal bones, five metacarpal bones, and 14 phalanges, plus the sesamoid bones, the number of which varies from person to person. [2]

From an engineering perspective, the hand is structured in "arches": one longitudinal arch along the wrist and two transverse arches that help distribute the load and shape the grip. The transverse arch at the level of the wrist bones simultaneously forms the bony foundation of the carpal tunnel and protects the important structures that lead to the fingers. [3]

The clinical value of this architecture is that it explains typical problems: fractures of individual bones, instability of ligaments, “pinched” nerves in narrow spaces, inflammation of tendon sheaths and wear of some joints under prolonged load. [4]

Table 1. What is included in the "skeleton of the hand"

Department	Compound	Quantity	Note
Wrist	Wrist bones	8	They form the frame of the wrist and the basis of the carpal tunnel
Metacarpus	Metacarpal bones	5	They form the "rays" of the hand, the base for the grip
Fingers	Phalanges	14	3 phalanges for the II-V fingers, 2 for the thumb
Additionally	Sesamoid bones	Variable	More common on the thumb

Table basis: description of the bones of the hand in StatPearls anatomical reviews. [5]

Wrist: 8 bones, 2 rows, and a "moving platform" biomechanics

The carpal bones are arranged in two rows. The proximal row (from the forearm side) contains the scaphoid, lunate, triquetral, and pisiform bones, while the distal row contains the trapezium, trapezoid, capitate, and hamate bones. [6]

The wrist acts as a mobile platform between the forearm and metacarpus. Small movements at several intercarpal joints combine to significantly contribute to overall hand mobility, especially when combined with flexion and extension at the wrist joint. [7]

An important feature is the transverse arch of the carpal bones. It forms the "floor" of the carpal tunnel, and the roof of this tunnel is the flexor retinaculum (transverse carpal ligament). This structure protects the finger flexors and the median nerve, but makes the area vulnerable to compression neuropathy when pressure within the tunnel increases. [8]

The blood supply to individual carpal bones varies, and this affects the risk of complications after fractures. For the scaphoid, the blood supply is particularly important because it often comes from the distal portion, making the proximal portion more vulnerable to disruption during a fracture, increasing the risk of nonunion and avascular necrosis. [9]

Table 2. Wrist bones and clinical "accents"

Bone	Row	Key role	What is important in the clinic
Scaphoid	Proximal	Connects rows, participates in the load	Risk of complications in fracture healing due to the peculiarities of the blood supply
Crescent Moon	Proximal	Central support of the proximal row	Important in assessing wrist stability
Triangular	Proximal	Contributes to the ulnar portion of the wrist	May be involved in injuries to the elbow margin
Pisiform	Proximal	Sesamoid bone in tendon	May cause local pain when overloaded
Trapezoid	Distal	The base of the joint at the base of the thumb	A common area of arthrosis is at the base of the big toe.
Trapezoidal	Distal	Stabilizes the radial part of the wrist	Usually gets injured less often
Capitate	Distal	The largest and most central	Important for intercarpal kinematics
Hook-shaped	Distal	Elbow edge support, "hook"	The hook can be a site of fractures and pain in athletes.

Basics: Anatomy of the carpal bones and their role, plus clinical comments on the scaphoid and arthrosis of the base of the thumb.[10]

Metacarpus and fingers: the rays of the hand, thumb opposition and precision of movement

The metacarpus consists of five metacarpal bones, which form the framework of the palm and provide the basis for grasping movements. Each metacarpal bone has a base, a shaft, and a head; the heads form the "knuckles" and participate in the metacarpophalangeal joints. [11]

The thumb is unique among the fingers: it has two phalanges, and its key functional advantage comes from the joint at the base of the thumb, between the trapezium and the first metacarpal. The saddle-shaped shape of this joint allows for thumb opposition and enables the precise pinching movements that almost define "human" hand function. [12]

The phalanges of the second through fifth fingers are represented by three bones (proximal, middle, and distal). This segmentation allows for movement to be distributed across multiple joints and allows for precise fingertip positioning, which is important for writing, handling small objects, and coordinating grips. [13]

From a practical standpoint, it is the "point at the base of the thumb" that often becomes problematic when worn: osteoarthritis of this joint is a common cause of pain at the base of the thumb, especially with a pinch grip and repetitive strain. [14]

Table 3. Main joints of the hand and their movements

Articular zone	Example of a joint	Basic movements	Functional meaning
Wrist	Forearm and proximal row of wrist	Flexion, extension, abduction, adduction	Positioning the brush as a "platform"
Intercarpal	Between the wrist bones	Small sliding movements	They increase mobility and stability in total.
Carpometacarpal	Distal carpal row and metacarpal bones	Sliding, saddle-shaped at the thumb	Palm Formation and Thumb Opposition
Metacarpophalangeal	Metacarpal bones and proximal phalanges	Flexion, extension, abduction, adduction	Adjusting the finger position when gripping
Interphalangeal	Between the phalanges	Flexion, extension	Precise fingertip control

The anatomical basis of the joints of the hand and the role of the joint at the base of the thumb are described in StatPearls reviews and the Proceedings of the American Academy of Orthopaedic Surgeons. [15]

Ligaments, fibrocartilaginous complexes, and tendons: what holds the hand together

The hand would be unstable without ligaments. The intercarpal ligaments play a key role in the wrist, holding the bones in proper alignment under load and preventing pathological "slippage" of the carpal rows. This is why, when a wrist injury occurs, it's not the bone but the ligaments that hurt, and a standard X-ray may not reveal a fracture. [16]

The triangular fibrocartilaginous complex on the ulnar side of the wrist deserves special attention. It acts as a stabilizer and "pad" between the ulna and carpal bones, contributing to load distribution and stabilization of the distal radioulnar joint. It is one of the structures often damaged by forced ulnar deviation of the wrist and by degenerative changes. [17]

The flexor and extensor tendons connect the forearm muscles to the bones of the hand. The "pulley system" of the fingers is particularly important for the flexors: the annular and cross retinacula hold the tendons close to the bone to ensure strong flexion without "stretching." A malfunction of the tendon glide in the area of the first annular retinaculum often underlies the phenomenon of "trigger finger." [18]

The flexor retinaculum (transverse carpal ligament) serves a dual purpose: it stabilizes the flexor tendons and forms the roof of the carpal tunnel, but when the tissue thickens or pressure within the tunnel increases, it can compress the median nerve. Therefore, the anatomy of the flexor retinaculum is directly related to carpal tunnel syndrome, the most common form of compression neuropathy in the upper extremity. [19]

Table 4. "Stabilizers" of the hand and what happens when they are damaged

Structure	Where is it located?	Main function	Typical clinical signal
Intercarpal ligaments	Between the wrist bones	Wrist Row Stability	Pain and instability without visible fracture
Triangular fibrocartilaginous complex	Ulnar edge of the wrist	Load stabilization and distribution	Pain along the ulnar edge of the wrist, increasing with exertion
Flexor retinaculum	Palmar surface of the wrist	Carpal tunnel roof, flexor retinaculum	Numbness in the median nerve area due to compression
Ring finger retainers	Along the fingers	Tunnel for flexor tendons	Clicking and locking motion in stenosing tenosynovitis
Tendon sheaths	Palm and fingers	Sliding tendons	Pain, swelling, and gliding problems due to inflammation

Background: Triangular fibrocartilaginous complex and carpal ligament injuries, flexor retinaculum, and mechanics of stenosing tenosynovitis. [20]

Nerves and vessels of the hand: why the hand is sensitive and where "tunnel" problems most often occur

The hand requires a precise blood supply because its tissues are constantly working and must recover quickly after exertion. In the wrist, blood flow is determined by the radial and ulnar arteries and their anastomoses, which form the palmar and dorsal arches. This provides "backup routes" for blood flow, but individual bones and areas may remain vulnerable to injury. [21]

The innervation of the hand is distributed among the median, ulnar, and radial nerves. The median nerve is particularly important for sensation in the radial portion of the hand and for the function of the muscles of the hallucis extensor digitorum, and also passes through the carpal tunnel in close proximity to the 9 flexor tendons. [22]

Carpal tunnel syndrome occurs when the median nerve is compressed within this narrow space. Current clinical guidelines from the American Academy of Orthopaedic Surgeons emphasize that the CTS 6 clinical tool can be used for diagnosis in place of routine ultrasound and electrophysiological testing in all patients and also indicate that corticosteroid administration does not provide long-term improvement. [23]

In addition to the carpal tunnel, there is also the ulnar canal at the wrist (Guyon's canal), as well as separate compartments on the dorsal surface where the extensor tendons pass. These anatomical "corridors" are important for the differential diagnosis of pain, numbness, and weakness, as similar complaints can have different levels of compression and different causes. [24]

Table 5. Key "channels" of the brush and what passes through them

Anatomical space	Borders	Content	Why is it clinically important?
Carpal tunnel	Carpal bones below, flexor retinaculum above	Median nerve and 9 flexor tendons	Frequent compression of the median nerve
Ulnar canal at the wrist	Fascial and bony structures of the elbow margin	Ulnar nerve and vessels	Numbness and weakness along the ulnar edge of the hand
Dorsal extensor compartments	Extensor retinaculum and bony grooves	Extensor tendons	Pain in tenosynovitis and overuse
Flexor tendon tunnel in the finger	Ring retainers	Flexor tendon	Clicking and locking of the finger in stenosing tenosynovitis

Basis: anatomy of the carpal tunnel and flexor retinaculum, clinical features of stenosing tenosynovitis and approaches to assessing soft tissue injuries of the hand. [25]

Common hand problems and modern diagnostics: trauma, pain, numbness

In hand and wrist injuries, radiography is usually the initial imaging modality. If a fracture is not visible on the initial imaging, but clinical suspicion remains, current American College of Radiology criteria recommend further imaging options: repeat radiography in 10-14 days, computed tomography (CT) scanning, or magnetic resonance imaging (MRI), depending on the clinical need. [26]

The scaphoid bone deserves special attention: a fracture of this bone often occurs with a fall on an outstretched hand and can cause pain at the base of the thumb. The American Academy of Orthopaedic Surgeons emphasizes that, due to the peculiarities of the scaphoid's blood supply, healing complications are more common than with fractures of some other wrist bones, so early recognition and appropriate immobilization or surgical intervention are essential. [27]

Chronic pain at the base of the thumb is often diagnosed as osteoarthritis of the joint at the base of the thumb. This joint is the functional "center" of opposition, so wear of its cartilage is particularly noticeable with pinch and force grips, and complaints are typically aggravated by everyday tasks such as opening lids and holding objects. [28]

Clicking and locking of the finger is typically caused by stenosing tenosynovitis, in which the flexor tendon passes through a narrowed area at the base of the finger and begins to "stick." Clinical materials from the American Academy of Orthopaedic Surgeons describe the characteristic symptoms, and current treatment reviews emphasize the effectiveness of basic measures and injection and surgical methods when indicated. [29]

In cases of numbness and tingling in the median nerve region, the carpal tunnel remains the key anatomical "location." The American Academy of Orthopaedic Surgeons guidelines for carpal tunnel syndrome emphasize the role of standardized clinical assessment and clarify that corticosteroid administration does not provide long-term improvement, and that results after mini-access and endoscopic tunnel release are comparable in patient-reported outcomes. [30]

Table 6. Imaging Choices for Hand and Wrist Injuries

Scenario	What do they usually do first?	What is considered next if suspicion remains?
Acute blunt trauma	X-ray	Repeated radiography after 10-14 days, computed tomography, magnetic resonance imaging
X-ray shows a fracture, but ligament or tendon damage is suspected.	Radiography plus clinical assessment	Magnetic resonance imaging, ultrasound examination according to the task
Suspected foreign body in soft tissue, radiography is negative	X-ray	Computed tomography, magnetic resonance imaging, ultrasound examination according to the task

Basis: American College of Radiology criteria for acute hand and wrist trauma. [31]