Wrist and Hand Bones Quizzes

The Carpal Bones

Names and Arrangement

The wrist consists of a proximal row and a distal row of carpal bones, each containing four bones.

From lateral to medial, the proximal row consists of the scaphoid, lunate, triquetrum, and pisiform bones.

From lateral to medial, the distal row consists of the trapezium (meaning “table”), trapezoid (“resembling a table”), capitate (“head-shaped”), and hamate (“hooked”) bones. The hamate has a prominent anterior projection called the hook of the hamate, which serves three essential functions:

• acts as a pulley for tendons that move the ring and little fingers,
• helps form passageways for nerves and blood vessels, and
• provides attachment points for muscles and ligaments important for grip strength and hand dexterity.

Attachments and Articulations

Ligaments connect the proximal carpal bones, creating a convex surface that articulates with the concave distal end of the radius to form the radiocarpal joint.

The radius articulates directly with the scaphoid and lunate and indirectly with the triquetrum through an intervening articular disc. The radiocarpal joint allows flexion (forward), extension (backward), and side-to-side movements of the hand.

The ulna does not articulate with the proximal carpal row. Instead, these carpal bones articulate with a fibrocartilaginous disc that cushions and stabilizes the wrist.

Ligaments also bind the four distal carpal bones, which articulate with the metacarpals.

The Carpal Tunnel

A cross-section of the wrist shows that the carpal bones are arranged in a U-shaped formation. The flexor retinaculum ligament extends from the trapezium and scaphoid bones on the lateral side of the wrist to the hamate and pisiform bones on the medial side. Together, the ligament and the bones create an enclosure known as the carpal tunnel, which allows flexor tendons and the median nerve to pass through.

Overuse of the muscles or injury to this area can cause inflammation that compresses the nerve. This condition, known as carpal tunnel syndrome, causes pain, numbness, and muscle weakness. Because the carpal tunnel is a rigid space, even small increases in tissue volume can significantly increase pressure on the median nerve.

The Metacarpal Bones

Names, Arrangement, and Articulations

Five metacarpal bones support the palm and are numbered 1 through 5, starting with the thumb side.

At their proximal ends, each metacarpal bone forms a carpometacarpal joint with a carpal bone in the distal row. The thumb carpometacarpal joint, formed by the first metacarpal and the trapezium bones, is the most flexible. The articulating surface of each bone is saddle-shaped, meaning it is concave in one direction and convex in the perpendicular direction. The saddle-shaped articulating surfaces fit together at right angles and are complementary. One surface’s concavity matches the other’s convexity, and vice versa.

This reciprocal concavo-convex relationship increases the thumb’s flexibility, including a motion called opposition. During this motion, the thumb moves forward (anteriorly) from the palm and sideways (medially) toward the tips of the other fingers, allowing the hand to grasp and manipulate objects.

Anterior View of the Right Wrist and Hand

The rounded distal ends of the metacarpal bones connect with the proximal row of phalanges to form the metacarpophalangeal joints, commonly known as the knuckles. These joints enable bending, spreading (abduction/adduction), and curling (flexion) of the fingers, which are essential for gripping and hand function.

The Phalanges

Names and Arrangement

The fingers and thumb together contain 14 bones, called phalanges (singular: phalanx), named after the ancient Greek phalanx (a column-like formation of soldiers arranged in tight rows). The thumb (pollex) is digit number 1 and has two phalanges: a proximal phalanx and a distal phalanx. Digits 2 (index finger) through 5 (little finger) each have three phalanges: the proximal, middle, and distal phalanges. An interphalangeal joint is one of the articulations between adjacent phalanges of the digits.