Hand Osteology/Arthrology

How many distal phalanges are there?

5

How many middle phalanges are there?

4

How many proximal phalanges are there?

5

How many metacarpals are there?

5

What is a ray composed of?

metacarpal + phalanges for each digit

Each metacarpal and phalanx has a

base and head

Base

proximal end

Head

distal end

Carpometacarpal (CMC) joints

bases of metacarpals articulate with distal end of carpals distal row

CMC thumb

saddle joint

2df; flexion/extension + abduction/adduction

CMC Index and Long

gliding joints

rigid, stable central pillar

very little/no movement

CMC Ring

gliding joint

1df; slight flexion/extension

CMC Pinky

gliding joint

2df; slight flexion/extension + opposition/reposition

Opposition

combination of thumb CMC abduction, flexion, and medial rotation

brings pad of thumb toward pads of fingers

Reposition

return to anatomic position

combination of thumb CMC adduction, extension, and lateral rotation

Metacarpophalangeal (MCP) Joints

located between the head of metacarpal and base of proximal phalanx at each digit

Thumb MCP joint and Digits 2-5 MCP joint

ellipsoid, condyloid joint

2df; flexion/extension and adduction/abduction

Interphalangeal Joint (Thumb)

between head of proximal phalanx and base of distal phalanx

DIP (Distal interphalangeal) joints

digits 2-5

between heads of middle phalanges and bases of distal phalanges

PIP (Proximal interphalangeal) joints

digits 2-5

between heads of proximal phalanges and bases of middle phalanges

All IP joints are ____ and have ___ degree of freedom

hinge joints; 1

Arches of the Hand

describes natural concavity of palmar surface of hand

the concavity changes shape during grasp and prehension tasks

each arch has a keystone that is essential for its stability

Longgitudinal arch

along 3rd ray

keystone → 2nd and 3rd MCP joints

Proximal Transverse Arch

level of CMC joints (fixed arch)

keystone → capitate

Distal Transverse Arch

level of MCP joints (mobile arch)

keystone → 2nd and 3rd MCP joints

Arched framework is supported by

intrinsic hand muscles