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Carpal bones: want to learn more about it?

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Carpal bones

The carpus is the anatomical term for the wrist which connects the radius and ulna of the forearm with the metacarpal bones of the hand. It is comprised of eight individual carpal bones that are seated in two neat rows of four. The proximal row of carpal bones, as seen in a lateral to medial direction on the palmar surface, include:

  • the scaphoid bone
  • the lunate bone 
  • the triquetral bone 
  • the pisiform bone

The distal row, as seen from the same viewpoint as above, includes:

  • the trapezium bone
  • the trapezoid bone 
  • the capitate bone
  • the hamate bone

Each carpal bone has its own unique shape and is multifaceted, giving it the ability to articulate with several bones, both in the same row and in the opposing row as well as with the bones of the hand and the antebrachial region. As a whole, the carpus on its carpal surface is convex proximally and concave distally, whereas on its palmar surface it is simply concave.

Key facts about the carpal bones
Scaphoid Superficially - anatomical snuff box; Proximally - radius; Distolaterally - trapezium;' Distomedially - trapezoid; Superomedially - lunate; Inferomedially - capitate 
Lunate Laterally - scaphoid, Medially - triquetrum, Inferiorly - capitate 
Triquetrum Distomedially - pisiform, Inferiorly - hamate, Laterally - lunate
Pisiform Dorsally - triquetrum; Lies within the tendon of flexor carpi ulnaris
Trapezium Medially - trapezoid; Superiorly - scaphoid; Inferolaterally - first metacarpalInferomedially - second metacarpal
Trapezoid Proximally - scaphoid bone; Laterally - trapezium; Medially - capitate; Distally - second metacarpal
Mnemonic: 'TrapeziUM is by the thUMB, trapezOID is by its SIDE
Capitate Proximally - lunate; Distally - third metacarpal; Laterally - trapezoid; Medially - hamate
Hamate Palpable due to the hamulus
Mnemonic Sally Left The Party To Take Cathy Home
( Scaphoid, Lunate, Triquetrum, Pisiform, Trapezium, Trapezoid, Capitate, Hamate)
Clinical Fractures, Carpal Tunnel Syndrome

The carpal tunnel is formed on the inside of the wrist due to this concavity and is covered by the flexor retinaculum, which is an osteofibrous sheath.

At birth, the carpus is cartilaginous, however during the first year and up, until twelve years of age, it undergoes a slow ossification process. It should be noted that many anatomical variants and accessory bones have been discovered, however only a central bone, a styloid bone, a secondary pisiform bone or a secondary trapezoid bone are generally considered to be so. This article will now discuss the individual carpal bones in detail, as well as highlight the potential pathological conditions that can affect the wrist.

  1. The proximal row of carpal bones
    1. Scaphoid bone
    2. Lunate done
    3. Triquetral bone
    4. Pisiform bone
  2. The distal row of carpal bones
    1. Trapezium bone
    2. Trapezoid bone
    3. Capitate bone
    4. Hamate bone
  3. Mnemonic
  4. Clinical aspects
    1. Scaphoid bone fracture
    2. Carpal tunnel syndrome
  5. Sources
+ Show all

The proximal row of carpal bones

Scaphoid bone

The scaphoid bone is the largest carpal bones of the proximal row and it lies beneath the anatomical snuff box. From a palmar view, it is surrounded on the proximal side by the radius, on the distolateral side by the trapezium bone and on the distomedial side by the trapezoid bone. Superomedially, it articulates with the lunate bone and inferomedially with the capitate bone. On the palm of the hand, its tubercle is easily palpable as it sits subcutaneously.

The blood vessels that supply the carpal bones enter the wrist along the lateral roughened surface of the scaphoid bone.

Lunate done

The next two proximal carpal bones, namely the lunate bone and the triquetral bone articulate with the head of the radius, which is known as the carpal articular surface. 

The lunate bone is a crescent shaped structure that has a large proximal articular surface which relates to the radial bone and its articular disk. It sits medially to the scaphoid bone, superior to the capitate bone and lateral to the triquetral bone. It may also sometimes come into contact with the hamate bone at its inferomedial angle.

Triquetral bone

The triquetral bone is shaped like a pyramid and, from a palmar perspective, its apex points disto-medially towards the pisiform bone, which is positioned upon its palmar facet. It sits upon the hamate bone, which is in the distal row of carpal bones and its base faces laterally and communicates with the lunate bone.

Pisiform bone

Lastly, the pisiform bone is the most medial proximal carpal bone from a palmar stance. It is also the smallest of all the carpal bones and classified as a sesamoid bone. Its dorsal surface is faceted, allowing it to articulate with the ventral surface of the triquetral bone. It is palpable and lies within the tendon of the flexor carpi ulnaris.

Carpal bones (anterior view)

The distal row of carpal bones

Trapezium bone

The trapezium is the first and most lateral of the distal row of carpal bones when the hand is viewed from its palmar surface. On the palmar aspect of the bone, there is a palpable tubercle and on its medial side runs a groove that holds the tendon of the flexor carpi radialis. The trapezium bone is bordered medially by the trapezoid bone and superiorly by the scaphoid bone. Inferolaterally, its main articulation is with the first metacarpal bone via a saddle shaped facet. Inferomedially however, it sometimes also articulates with the second metacarpal bone.

Trapezoid bone

The trapezoid bone may look very small in comparison to the other bones from a palmar aspect, however it is much wider on its dorsal side. It communicates via its proximal facet with the scaphoid bone, laterally with the trapezium bone, medially with the capitate bone and its distal facet allows it to articulate with the second metacarpal bone.

How can you remember which is more lateral between the trapezium and trapezoid? Here's now!

  • 'TrapeziUM is by the thUMB, trapezOID is by its SIDE'

Worried about how you're going to remember all the carpal bones? Look no further than our interactive carpal bone quizzes and labeling activities - they'll help you consolidate information fast and effectively. 

Capitate bone

The capitate bone is the largest of all the carpal bones, both proximally and distally. It is surrounded by the lunate bone proximally, the third metacarpal bone distally, the trapezoid bone laterally and the hamate bone medially.

Hamate bone

The last of the eight carpal bones and the distal row is the hamate bone. It is subcutaneously palpable, due to the hamulus, which is a bony notch on its palmar aspect and curves laterally. It exists in aid of the flexor digiti minimi brevis and the pisohamate ligament.

The hamate bone is surrounded from a proximolateral direction by the lunate bone and a proximomedial direction by the triquetral bone. Laterally, it communicates with the capitate bone and, distally, it articulates with both the fourth and fifth metacarpal bones.


A useful mnemonic in order to remember the order of the carpal bones from lateral to medial, in the proximal row and then the distal row is the following: 

Sally Left The Party To Take Cathy Home

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

Carpal bones: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

What do you prefer to learn with?

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

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