Bones of the hand: 27 bones of the wrist, palm and fingers

Each upper limb has 30 bones: the humerus, the ulna and radius, 8 carpal bones, 5 metacarpal bones and 14 phalanges. The wrist and hand account for 27 of them (8 + 5 + 14). (OpenStax Anatomy and Physiology 2e, 8.2: Bones of the Upper Limb.)

The bones fall into three groups from proximal to distal: the carpals in the wrist, the metacarpals in the palm and the phalanges in the digits. The carpals are a set of eight irregular bones, and each of the five metacarpals is related to one digit. (TeachMeAnatomy: Bones of the Hand.)

Both hands together therefore contain 54 of these bones. The standard count leaves out the small sesamoid bones, whose number varies from person to person. (Chen W et al. Prevalence and variation of sesamoid bones in the hand. Int J Clin Exp Med 2015.)

The carpal bones sit in two rows of four. Listed from lateral (thumb side) to medial, the proximal row is the scaphoid, lunate, triquetrum and pisiform, and the distal row is the trapezium, trapezoid, capitate and hamate. (OpenStax Anatomy and Physiology 2e, 8.2: Bones of the Upper Limb.)

OpenStax offers the mnemonic "So Long To Pinky, Here Comes The Thumb": it runs across the proximal row from thumb to little finger and then back across the distal row from the little finger to the thumb (scaphoid, lunate, triquetrum, pisiform, hamate, capitate, trapezoid, trapezium). (OpenStax Anatomy and Physiology 2e, 8.2: Bones of the Upper Limb.)

Kenhub uses a different mnemonic that keeps both rows in the lateral to medial order: "She Likes To Play, Try To Catch Her" (scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate). Use whichever matches the order your course expects. (Kenhub: Carpal bones.)

Together the carpals form an arch whose hollow faces the palm. The flexor retinaculum stretches across the arch to form the carpal tunnel, through which nine flexor tendons and the median nerve pass. Compression of the median nerve in this tunnel is carpal tunnel syndrome. (OpenStax Anatomy and Physiology 2e, 8.2: Bones of the Upper Limb.)

The scaphoid is the largest bone of the proximal row and is boat-shaped. Its palmar tubercle can be felt under the skin, and the bone lies in the floor of the anatomical snuffbox. It articulates with the radius, trapezium, trapezoid, lunate and capitate. (Kenhub: Carpal bones.)

The lunate, named for its crescent moon shape, sits between the scaphoid and triquetrum. It meets the radius and the articular disc of the distal radioulnar joint above and the capitate below. The triquetrum (triquetral bone) is pyramid-shaped, lies medially and carries a small facet for the pisiform. (Kenhub: Carpal bones.)

The pisiform is a tiny, pea-shaped bone on the palmar surface of the triquetrum. It is a sesamoid bone embedded in the tendon of flexor carpi ulnaris, and it is easy to feel in the palm on the little finger side of the wrist. (Kenhub: Carpal bones.)

The scaphoid and lunate articulate with the radius at the wrist (radiocarpal) joint. OpenStax also counts the triquetrum as part of this joint. The joint between the two carpal rows is the midcarpal joint. (OpenStax Anatomy and Physiology 2e, 8.2: Bones of the Upper Limb.)

The trapezium is the most lateral bone of the distal row. It articulates with the scaphoid, the trapezoid and the first and second metacarpals. The wedge-shaped trapezoid sits beside it and articulates with the second metacarpal. (Kenhub: Carpal bones.)

The capitate is the largest carpal bone. It sits in the middle of the distal row and articulates mainly with the third metacarpal, as well as with the trapezoid, scaphoid, lunate and hamate. (Kenhub: Carpal bones.)

The hamate is the most medial bone of the distal row and articulates with the fourth and fifth metacarpals. Its hook (hamulus) projects into the palm, forming the medial wall of the carpal tunnel and the lateral wall of the ulnar (Guyon's) canal. (Kenhub: Carpal bones.)

The five metacarpals form the skeleton of the palm. They are numbered 1 to 5 from the thumb to the little finger. Although they are short, they are classed as long bones, each with a proximal base, a shaft and a distal head. The heads form the knuckles when you make a fist. (Kenhub: Metacarpal bones.)

The bases articulate with the distal row of carpals at the carpometacarpal joints: the first with the trapezium through a saddle-shaped surface, the second with the trapezium, trapezoid and capitate, the third with the capitate, and the fourth and fifth with the hamate. (Kenhub: Metacarpal bones.)

The first metacarpal is the shortest and thickest and is rotated about 90 degrees medially relative to the others, so the thumb sits at an angle to the rest of the palm. The second has the longest shaft and the largest base, and the fifth is the smallest. (Kenhub: Metacarpal bones.)

Their mobility differs. The first metacarpal moves independently, the second and third are essentially immobile, and the fourth and fifth have a little movement that helps the hand cup around an object during a power grip. (OpenStax Anatomy and Physiology 2e, 8.2: Bones of the Upper Limb.)

There are 14 phalanges in each hand. Fingers 2 to 5 each have three: a proximal, a middle and a distal phalanx. The thumb has only two, a proximal and a distal phalanx. That gives 5 proximal, 4 middle and 5 distal phalanges. (Kenhub: Phalanges of the hand.)

Each phalanx has a proximal base, a shaft (body) and a distal head. The base of each proximal phalanx has a concave oval facet for the head of its metacarpal. The heads of the proximal and middle phalanges are pulley-shaped, and each distal phalanx ends in a rough distal tuberosity that supports the fingertip pulp. (Kenhub: Phalanges of the hand.)

Flexor digitorum superficialis attaches to the sides of the middle phalanges and flexes the proximal interphalangeal joints. Flexor digitorum profundus inserts into the bases of the distal phalanges of the fingers, and flexor pollicis longus into the distal phalanx of the thumb. The extensor expansion covers the back of the phalanges. (Kenhub: Phalanges of the hand.)

The bases of the proximal phalanges receive several muscles directly, including the lumbricals, the interossei and the thenar and hypothenar muscles. (Kenhub: Phalanges of the hand.)

Each finger has a metacarpophalangeal (MCP) joint between the metacarpal head and the proximal phalanx, a proximal interphalangeal (PIP) joint and a distal interphalangeal (DIP) joint. The thumb has an MCP joint and a single interphalangeal joint. (Kenhub: Phalanges of the hand.)

These joints are of different synovial types. The radiocarpal joint and the MCP (knuckle) joints are condyloid joints, the interphalangeal joints are hinge joints, the intercarpal joints are plane joints, and the first carpometacarpal joint at the base of the thumb is a saddle joint. (OpenStax Anatomy and Physiology 2e, 9.4: Synovial Joints.)

The saddle joint at the base of the thumb allows opposition, which brings the tip of the thumb into contact with the tip of a finger. (OpenStax Anatomy and Physiology 2e, 9.5: Types of Body Movements.)

Sesamoid bones are not counted among the 27. The best known in the hand is the pisiform, which TeachMeAnatomy describes as a sesamoid bone formed within the tendon of flexor carpi ulnaris. (TeachMeAnatomy: Bones of the Hand.)

The other sesamoids of the hand are tiny bones on the palmar side of the metacarpophalangeal joints and, less often, of the thumb interphalangeal joint. In X-ray studies they are confirmed on oblique views of the hand. (Chen W et al. Prevalence and variation of sesamoid bones in the hand. Int J Clin Exp Med 2015.)

In a radiographic study of 850 adult hands from four hospitals in China, every thumb MCP joint had two sesamoid bones. Sesamoids were also seen at the index finger MCP joint in 60.8% of hands, at the little finger MCP joint in 59.1%, and at the thumb interphalangeal joint in 15.9%. They were rare at the middle and ring finger MCP joints. (Chen W et al. Prevalence and variation of sesamoid bones in the hand. Int J Clin Exp Med 2015.)

A Turkish multicentre X-ray study of 1,444 hands also found thumb MCP sesamoids in every person, on both sides. It reported lower figures at the index MCP joint (36.6% of hands) and similar figures at the little finger MCP joint (62.5%) and thumb interphalangeal joint (18.6%), so frequencies vary between populations. (Civan O et al. Sesamoid bones of the hand: a multicenter study. Jt Dis Relat Surg 2020.)

The BodyParts3D model used on this page does not include the sesamoid bones of the hand, so they are not shown in the 3D view.

The scaphoid is the most commonly fractured carpal bone, usually after a fall on an outstretched hand. The typical sign is pain and tenderness in the anatomical snuffbox. Its blood supply enters at the distal end, so a fracture across the waist can cut off the proximal part and lead to avascular necrosis. (TeachMeAnatomy: Bones of the Hand.)

OpenStax notes that because of this poor blood supply, scaphoid fractures heal slowly and carry a risk of bone death and later degenerative joint disease of the wrist. (OpenStax Anatomy and Physiology 2e, 8.2: Bones of the Upper Limb.)

A boxer's fracture is a break of the neck of the fifth metacarpal, typically from punching a hard object with a clenched fist. A Bennett's fracture is a fracture of the base of the first metacarpal that extends into the carpometacarpal joint of the thumb and often needs surgery. (TeachMeAnatomy: Bones of the Hand.)

Capitate

The largest carpal bone, with a rounded head.

Distal phalanx of index finger

The smallest, end bone of the index finger (second digit), supporting the fingertip and nail.

Distal phalanx of little finger

The smallest, end bone of the little finger (fifth digit), supporting the fingertip and nail.

Distal phalanx of middle finger

The smallest, end bone of the middle finger (third digit), supporting the fingertip and nail.

Distal phalanx of ring finger

The smallest, end bone of the ring finger (fourth digit), supporting the fingertip and nail.

Distal phalanx of thumb

The end bone of the thumb, supporting the nail and pulp.

Fifth metacarpal bone

The little finger metacarpal. One of the five long bones of the palm.

First metacarpal bone

The thumb metacarpal, shorter and stouter than the others. One of the five long bones of the palm.

Fourth metacarpal bone

The ring finger metacarpal. One of the five long bones of the palm.

Hamate

A wedge-shaped carpal bone of the distal row with a hook.

Lunate

A crescent-shaped carpal bone in the middle of the proximal row.

Middle phalanx of index finger

The middle of the three phalanges of the index finger (second digit).

Middle phalanx of little finger

The middle of the three phalanges of the little finger (fifth digit).

Middle phalanx of middle finger

The middle of the three phalanges of the middle finger (third digit).

Middle phalanx of ring finger

The middle of the three phalanges of the ring finger (fourth digit).

Pisiform

A small, pea-shaped carpal bone on the palmar side of the triquetrum.

Proximal phalanx of index finger

The longest of the three phalanges of the index finger (second digit), nearest the palm.

Proximal phalanx of little finger

The longest of the three phalanges of the little finger (fifth digit), nearest the palm.

Proximal phalanx of middle finger

The longest of the three phalanges of the middle finger (third digit), nearest the palm.

Proximal phalanx of ring finger

The longest of the three phalanges of the ring finger (fourth digit), nearest the palm.

Proximal phalanx of thumb

The first of the thumb's two phalanges.

Scaphoid

The largest bone of the proximal carpal row, shaped like a boat.

Second metacarpal bone

The index finger metacarpal, usually the longest. One of the five long bones of the palm.

Third metacarpal bone

The middle finger metacarpal. One of the five long bones of the palm.

Trapezium

A four-sided carpal bone at the thumb side of the distal row.

Trapezoid

A small wedge-shaped carpal bone of the distal row.

Triquetral

A pyramid-shaped carpal bone on the ulnar side of the proximal row.