Each finger except the thumb consists of three bones – the proximal, middle, and distal phalanx. The thumb has only two phalanges – the proximal and the distal.

Icon of crossfade image
Bones of the hand. The palmar view Phalanges. The palmar view
Phalanges in situ. The palmar view.
Icon of crossfade image
Bones of the hand. The dorsal view Bones of the figers. The dorsal view
Phalanges in situ. The dorosal view.

Sesamoid bones (ossa sesamoidea) seen on both previous pictures are the rounded bones embedded in the muscle's tendons to protect them from excessive friction and redirect the tendon's attachment vector, so the muscle action is more effective1. These bones are almost invariably present in front of the first metacarpophalangeal joint. They are also frequently observed in front of the fifth metacarpophalangeal joint and the thumb's interphalangeal joint.2

  • 1 Amar E, Rozenblat Y, Chechik O. Sesamoid and accessory bones of the hand–an epidemiologic survey in a Mediterranean population. Clin Anat. 2011;24(2):183-187.
  • 2 Yammine K. The prevalence of the sesamoid bones of the hand: a systematic review and meta-analysis. Clin Anat. 2014;27(8):1291-1303.
  • Icon of crossfade image The topography of the third metacarpal bone
    3rd metacarpal bone in situ The topography of the third metacarpal bone
    The dorsal, lateral, and palmar aspect of the proximal, middle, and distal phalanx of the 3rd finger. The distal phalanx's tuberosity is larger at the palmar surface as it serves for the attachment of the tactile pads.
    The list of terms: Phalanx proximalis – Proximal phalanx
    Phalanx media – Middle phalanx
    Phalanx distalis – Distal phalanx
    Caput phalangis – Head of the phalanx
    Trochlea phalangis – Trochlea of phalanx
    Corpus phalangis – Body (shaft) of phalanx
    Basis phalangis – Base of phalanx
    Tuberositas phalangis distalis – Tuberosity of distal phalanx

    Icon of crossfade image Iso view of phalanges with the anatomical terminology markup
    Top iso view of the phalanges Top bottom view of the phalanges
    The phalanges of the 3rd finger
    Click an image to switch between the top- and bottom-oblique view. Note the shape of the congruent articular surfaces between phalanges (uniaxial, hinge-type joint). It differs from the ellipsoid-shaped metacarpophalangeal joint, providing bi-axial rotation of the proximal phalanx. The shape of the articular surface at the base (ellipsoid vs. bi-concave) is the main characteristic allowing to differentiate the proximal phalanx from the distal one.

    360° rotation of the hand bones
    First published: 12/Oct/2020
    Last update: 20/Dec/2020