Bones of the Wrist and Hand

Distal Forearm–Wrist Articulation

  • At the wrist joint the radius (not the ulna) is the main bone that articulates with the proximal carpal row.
  • Orientation in lab/exam questions is typically palmar (anterior) view, palm up.

Big-Picture Layout of the Hand

  • Three anatomical regions (proximal ➜ distal):
    • Carpals (wrist bones)
    • Metacarpals (palm)
    • Phalanges (fingers)

Carpal Bones – Overview

  • Total of 88 carpal bones arranged in 22 transverse rows of 44 each.
  • Systematic identification strategy: always start on the thumb (lateral/radial) side and name bones proximal row first, then distal row.
  • Path of naming: Thumb → Pinky across proximal row (1-2-3-4) then return to thumb and cross distal row (1-2-3-4).
Proximal Row (thumb ➜ pinky)
  1. Scaphoid – boat-shaped
  2. Lunate – crescent/moon-shaped
  3. Triquetrum – three-cornered
  4. Pisiform – pea-shaped (sits on top of triquetrum)
Distal Row (thumb ➜ pinky)
  1. Trapezium – distal to the thumb Metacarpal 11
  2. Trapezoid – medial to trapezium, smaller
  3. Capitate – largest, "head-shaped"
  4. Hamate – has a palpable "hook of hamate"
Mnemonics (pick the one that sticks)
  • "Some Lovers Try Positions That They Can’t Handle"
    • S = Scaphoid, L = Lunate, T = Triquetrum, P = Pisiform, T = Trapezium, T = Trapezoid, C = Capitate, H = Hamate
  • PG-rated option: "Stop Letting Those People Touch The Cadaver’s Hand"
Distinguishing Features & Clinical Pearls
  • Hook of Hamate
    • Palpable on medial palm; common fracture site when falling on an out-stretched hand or in sports using bats/clubs.
  • Pisiform
    • Easily felt on medial wrist; sesamoid bone within the flexor carpi ulnaris tendon.
  • Scaphoid
    • Most frequently fractured carpal; tenderness in anatomic snuff-box → high suspicion.
  • Radial vs. Ulnar deviation tests rely on scaphoid–lunate integrity.

Metacarpals

  • Five long bones numbered lateral (thumb) to medial (pinky): 1→51 \rightarrow 5.
  • Landmarks
    • Base (proximal) – articulates with distal carpals.
    • Shaft – diaphysis.
    • Head (distal) – forms knuckles; common injury site when striking an object ("boxer’s fracture" of Metacarpal 55).

Phalanges

  • Digits 2-5 each contain three phalanges:
    • Proximal, Middle, Distal.
  • The thumb (pollex) has only two: Proximal and Distal (no middle phalanx).
Joints & Functional Notes
  • Metacarpophalangeal (MCP) joints – between metacarpal heads and proximal phalanges (knuckles).
  • Interphalangeal (IP) joints
    • Thumb: a single IP joint.
    • Other digits: Proximal (PIP) & Distal (DIP) IP joints.

Naming Origins (etymology – helpful memory hooks)

  • Scaphoid = "skiff/boat" → resembles boat hull.
  • Lunate = "lunar" (moon).
  • Triquetrum = "three-cornered" triangular outline.
  • Pisiform = "pea-shaped" sesamoid.
  • Trapezium/Trapezoid = four-sided irregular figures.
  • Capitate = "head" – bulkier central bone.
  • Hamate = "hooked" – obvious hook process.

Quick-Fire Review Checklist

  • List proximal row from thumb: Scaphoid, Lunate, Triquetrum, Pisiform.
  • List distal row from thumb: Trapezium, Trapezoid, Capitate, Hamate.
  • Count carpals =8=8, metacarpals =5=5, phalanges per finger =3=3 (thumb =2=2).
  • Which bone is most often fractured in FOOSH? Scaphoid.
  • Palpable medial wrist bump? Pisiform (superficial) with hook of hamate just distal.
  • Knuckle = head of metacarpal at the MCP joint.

Practical & Clinical Connections

  • Proper hand positioning (radial vs ulnar deviation) assesses carpal alignment.
  • Occupational hazards: gripping tools (carpenters, golfers) → hamate stress fracture.
  • Anatomical knowledge essential for interpreting wrist X-rays and treating fractures.
  • Understanding sesamoid (pisiform) helps in carpal tunnel decompression planning.

Study Tips

  • Always orient the palm up when drilling bones; consistent orientation reinforces spatial memory.
  • Trace the mnemonic while physically palpating your own wrist/fake skeleton to link kinesthetic memory.
  • Test yourself by drawing the two rows as two arcs: proximal arc (concave toward radius), distal arc (fits metacarpal bases).
  • Relate bone names to shapes—visualization cements recall.