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Bones of the Hand

Ossa manus

For medical students2 min readUpdated 2026-10-10

The skeletal framework of the hand is a complex structure providing both structural support and exceptional mobility. Anatomically, it is divided into three major regions: the carpus (wrist), metacarpus, and digits (phalanges), each with unique structural features.

Carpus8 short (cancellous) bones arranged in 2 rows
ThumbContains only 2 phalanges, unlike the other digits
OssificationBegins with the distal row of the carpus
Capitate boneThe largest of all the carpal bones

Surfaces and Regions of the Hand

The hand has two main surfaces: the palm (palma manus) and the back of the hand (dorsum manus).

The skeletal framework of the hand is sequentially divided into three regions:

  1. Carpus (carpus)
  2. Metacarpus (metacarpus)
  3. Digits (digiti manus)

In anatomy, standard nomenclature is used for each digit:

Carpal Bones (Ossa carpi)

The wrist is formed by eight cancellous bones grouped into two rows. Conventionally, the bones in each row are counted from the lateral side (thumb) to the medial side (little finger).

Proximal row:

  1. Scaphoid (os scaphoideum)
  2. Lunate (os lunatum)
  3. Triquetrum (os triquetrum)
  4. Pisiform (os pisiforme) — a sesamoid bone embedded within a tendon.

Distal row:

  1. Trapezium (os trapezium)
  2. Trapezoid (os trapezoideum)
  3. Capitate (os capitatum) — the largest carpal bone.
  4. Hamate (os hamatum) — features a characteristic hook (hamulus ossis hamati).

On the palmar side of these bones, the carpal sulcus (sulcus carpi) is formed. Medially, it is bounded by the pisiform and the hook of the hamate. Laterally, its boundaries are formed by the tubercle of the scaphoid bone (tuberculum ossis scaphoidei) and the tubercle of the trapezium (tuberculum ossis trapezii).

Metacarpals and Phalanges

Metacarpal bones (ossa metacarpi I–V) are five short tubular bones. Each consists of a bulky base (basis ossis metacarpi) at the proximal end, a triangular shaft (corpus ossis metacarpi), and a distal head (caput ossis metacarpi) that articulates with the proximal phalanges. Notably, the first metacarpal bone (I) is the shortest and most robust.

Phalanges (phalanges digitorum manus) form the skeletal framework of the fingers. Digits II through V each possess three phalanges:

The exception is the thumb (pollex), which lacks a middle phalanx, consisting only of proximal and distal phalanges. Like the metacarpals, each phalanx features a base, shaft, and head. A distinct feature of the distal phalanges is the presence of a tuberosity at their tips (tuberositas phalangis distalis).

Ossification Process

The appearance of ossification centers in the carpal bones follows a specific pattern, initiating in the distal row and progressively extending to the proximal row.

The approximate chronological order of ossification is:

  1. Os capitatum and Os hamatum (the largest bones of the distal row) — from the 2nd month of prenatal development to 1–2 years of age.
  2. Os triquetrum — at 3–4 years.
  3. Os lunatum — at 4–5 years.
  4. Os scaphoideum — at 5–6 years.
  5. Os trapezium — at 6–7 years.
  6. Os trapezoideum — at 7–8 years.
  7. Os pisiforme — last to ossify, at 8–14 years.

Mnemonic

For practical exams, practice sketching the carpal bones freehand, clearly separating the 8 bones into proximal and distal rows while counting laterally from the thumb.

Frequently asked questions

Which intrinsic hand muscles originate from the hook of the hamate?

Two muscles of the hypothenar eminence originate from the hook of the hamate:

  • Flexor digiti minimi brevis (m. flexor digiti minimi brevis) — originates from the hook of the hamate and the flexor retinaculum; flexes the proximal phalanx of the 5th digit.
  • Opponens digiti minimi (m. opponens digiti minimi) — originates from the hook of the hamate (hamulus ossis hamati) and inserts on the ulnar border of the 5th metacarpal bone, opposing the little finger.
What neurovascular structures pass through the carpal tunnel (canalis carpalis)?

The only nerve passing through the carpal tunnel (canalis carpi) is the median nerve; no major blood vessels are considered part of its contents.

  • Median nerve (n. medianus) — lies superficially within the connective tissue among the tendons, directly beneath the flexor retinaculum (retinaculum musculorum flexorum).

In addition to the median nerve, the tunnel transmits the tendons of the flexor digitorum superficialis, flexor digitorum profundus, and the tendon of the flexor pollicis longus.

How many phalanges does the thumb have?

The thumb (pollex) has only two phalanges: a proximal and a distal phalanx. It lacks a middle phalanx.

What structures bound the carpal sulcus (sulcus carpi)?

Medially, the sulcus is bounded by the pisiform bone and the hook of the hamate. Laterally, it is bounded by the tubercles of the scaphoid and trapezium bones.

Which carpal bone ossifies last?

The pisiform bone (os pisiforme). Its ossification center appears last, approximately between 8 and 14 years of age.

To which bone classification does the pisiform bone belong?

The pisiform is classified as a sesamoid bone because it develops within the substance of a muscle tendon.

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