BONES OF THE

WRIST JOINT

The wrist

area b/w the hand and forearm.Made up of a group of short bones known

as the carpus or wrist bonesConsists of eight carpal bones which form

2 rows 4 proximal carpal bones 4 distal carpal bones

The proximal carpal bones (PCB) are :Scaphoid bone Lunate boneTriquetrumPisiform bone

The distal carpal bones (DCB) are :TrapeziumTrapezoid boneCapitate boneHamate bone

THE PROXIMAL CARPAL BONES

Scaphoid bone

Boat –shaped

PCB on the lateral border of the wrist

The carpal bone closest to the styloid process of

the radius

Has a prominent tubercle on its lateral palmar

surface directed anteriorly

Lunate bone

Comma-shaped

Articulates with the radius like the

scaphoid bone

Medial to the scaphoid bone

Triquetrum

Small 3-sided shaped boneMedial to lunate boneArticulates with the articular disc separating

the ulnar head from the wrist

Pisiform bone

Small, pea-shapedArticulates with ant. surface of triquetrum

THE DISTAL CARPAL BONES

Trapezium

Irregular 4-sided bone

Lateral bone of the distal row

Has a distinct tubercle on its palmar surface

that projects ant

Proximal surface articulates with scaphoid bone

Articulates with metacarpal of thumb

Trapezoid bone

4-sided wedge shaped

Lies medial to the trapezium

Like the trapezium it has aproximal

articulation with the scaphoid

Capitate bone

Largest carpal bone Sits b/w trapezoid bone and the hamate bone Articulates with the base of metacarpal III

Hamate bone

Has a hook on its palmar surface that projects ant.

Medial distal carpal bone

To remember…Sam- Scaphoid PCB FROM

Likes - Lunate LATERAL TO

To – Triquetrum MEDIAL

Push - Pisiform

The - Trapezium

Toy – Trapezoid DCB FROM

Car – Capitate LATERAL TO

Hard- Hamate MEDIAL

ARTICULAR SURFACES

Carpals have numerous articular surfaces

1. They articulate with each other

2. DCB articulate with metacarpals of the digits

3. The expansive proximal surfaces of the scaphoid and lunate articulate with the radius to form the most of the wrist joint

THE WRIST JOINT

Synovial joint (ellipsoid joint) b/w distal end

of the radius and the articular disc

overlying the distal end of the ulna, the

scaphoid, lunate & triquetrum

The articular surfaces of the carpals form

an oval shape with a convex contour

with the corresponding concave surface

of the radius and articular disc

The capsule of the wrist joint is reinforced by palmar

radiocarpal, palmar ulnocarpal, and dorsal

radiocarpal ligaments. In addition, radial and ulnar

collateral ligaments of the wrist joint span the

distance between the styloid processes of the radius

and ulna and the adjacent carpal bones. These

ligaments reinforce the medial and lateral sides of

the wrist joint and support them during flexion and

extension.

CARPAL JOINTS

The synovial joints between the carpal bones share

a common articular cavity. The joint capsule of the

joints is reinforced by numerous ligaments.

Although movement at the carpal joints

(intercarpal joints) is limited, they do contribute to

the positioning of the hand in abduction, adduction,

flexion, and, particularly, extension.

Movements of the wrist joint

The wrist joint allows movement around two axes

abduction and adduction

flexion and extension

NOTE: Because the radial styloid process extends

further distally than does the ulnar styloid process, the

hand can be adducted to a greater degree than it can

be abducted.

REFERENCES

Gray’s Anatomy for students; Drake et al ; Elsevier; 2005

Principles of anatomy and physiology; Tortora Gerard; 3rd edition; New York. John Wiley, 2003

Fundamentals of Anatomy and Physiology; Martini F; USA; Benjamin Cummings; 2004

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