Upper Extremity Analysis of the Wrist - Fundamentals and Assessment Tools for Occupational Ergonomics - page 842

Middle finger

Ring finger III

Index finger

IV

II

Little finger
V

Distal phalanx

Distal interphalangeal
(DIP) joint

Medial phalanx

Proximal interphalangeal
(PIP) joint Proximal phalanx

I Thumb

Metacarpophalangeal
(MCP) joint

Metacarpals

Carpometacarpal (CMC) joint

Trapezoid

Hamate

Trapezium

Pisiform

Scaphoid

Triquetrum

Capitate

Lunate

Ulna

Radius

FIGURE 45.1 Bones and joints of the right hand (palmar view).

articulation with the base of the corresponding phalanges. Interosseous muscles and extensor tendons
run along the concave side and the large and smooth dorsal surface of the shaft, respectively, while
the distal ends have a grooved volar surface for the flexor tendons (Nordin and Frankel, 2001).
There are three phalanges for each digit and two for the thumb for a total of 14 bones. They are labeled
proximal, middle, and distal phalanges (with the middle one missing in the thumb), according to their
positions and become progressively smaller. The heads of the proximal and middle phalanges are bicon-
dylar, facilitating flexion, extension, and circumduction. The shafts are semicircular in cross section (the
palmar surface being almost flat), as opposed to the cylindrical metacarpals. The axes of the distal pha-
langes of the index, ring, and little fingers are respectively deviated ulnarly, radially, and radially from the
axes of the middle phalanges (Gigis and Kuczynski, 1982).

45.1.2 Joints of the Hand and Wrist
There are four joints in each finger, in sequence from the proximal to distal: carpometacarpal (CMC),
metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints