Articulations of the Digits

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Anatomy > Gray's Anatomy of the Human Body > III. Syndesmology > 6k. Articulations of the Digits

Henry Gray (1821–1865). Anatomy of the Human Body. 1918.

Articulations of the Digits of the Hand

(Articulationes Digitorum Manus; Interphalangeal Joints)

The articulations of the fingers—specifically the interphalangeal joints—are a series of hinge joints that permit flexion and extension between the phalanges of the hand.

Articulations of the digits (posterior view)

Articulations of the digits (lateral view)

There are two interphalangeal joints in each finger:

• The proximal interphalangeal joint (PIP) – between the proximal and middle phalanges.
• The distal interphalangeal joint (DIP) – between the middle and distal phalanges.

The thumb, having only two phalanges, possesses a single interphalangeal joint.

Ligaments of the Interphalangeal Joints

Each interphalangeal joint is stabilized by three primary ligaments:

• Palmar ligament (volar plate): A thick, fibrocartilaginous band that reinforces the anterior side of the joint capsule and limits hyperextension.
• Collateral ligaments: Paired medial and lateral bands that provide lateral stability and help guide motion during flexion and extension.
• The extensor tendons serve the function of posterior ligaments, as the joints lack distinct posterior reinforcement.

Movements

The interphalangeal joints permit the following:

• Flexion: Bending the finger toward the palm.
• Extension: Straightening the finger from a flexed position.

Flexion is more pronounced at the proximal interphalangeal joint (PIP) than at the distal interphalangeal joint (DIP). Extension is restricted by the volar and collateral ligaments.

Muscles Acting on the Joints of the Digits

Metacarpophalangeal Joints (MCP)

• Flexion:

Flexor digitorum superficialis Flexor digitorum profundus Lumbricals Palmar interossei and dorsal interossei Flexor digiti minimi brevis (for little finger)

• Extension:

Extensor digitorum Extensor indicis Extensor digiti minimi

Interphalangeal Joints

• Flexion:

Flexor digitorum superficialis (acts on PIP) Flexor digitorum profundus (acts on PIP and DIP)

• Extension:

Lumbricals and interossei muscles (via their insertion into the extensor expansion) Extensor digitorum plays a limited role directly

Thumb Joints

• Flexion of MCP joint:

Flexor pollicis brevis Flexor pollicis longus

• Extension of MCP joint:

Extensor pollicis brevis

• Flexion of interphalangeal joint:

Flexor pollicis longus

• Extension of interphalangeal joint:

Extensor pollicis longus

Functional Importance

The interphalangeal and metacarpophalangeal joints are essential for precise hand movements, grasping, and manual dexterity. These joints are stabilized by a complex interplay of passive (ligaments) and dynamic (muscular) support systems. Disruption of any of these structures can result in impaired function, such as in cases of arthritis, tendon injury, or joint instability.

See Also

• Phalanges
• Hand
• Extensor mechanism of the hand
• Flexor tendons of the hand
• Interphalangeal joints of the foot

Gray's Anatomy

• Gray's Anatomy Contents
• Gray's Anatomy Subject Index
• About Classic Gray's Anatomy
• Glossary of anatomy terms

Anatomy atlases (external)

[1] - Anatomy Atlases

Adapted from the Classic Grays Anatomy of the Human Body 1918 edition (public domain)