Distal interphalangeal joints of hand

The distal interphalangeal (DIP) joints of the hand are the hingetype synovial joints located between the middle and distal phalanges of the index, middle, ring, and little fingers (digits 2-5). The thumb, having only two phalanges, has a single interphalangeal joint (IPJ) rather than a DIP joint.

Anatomy and Structure

Each DIP joint is stabilized by collateral ligaments, a volar plate. The extensor tendon (terminal tendon) inserts on the dorsal base of the distal phalanx, while the flexor digitorum profundus (FDP) tendon inserts on the volar base, making these the only two tendons that cross the DIP joint.

Biomechanics and Function

The DIP joints primarily allow flexion and extension, with a typical range of motion of approximately 080 degrees of flexion. They are subjected to the highest joint forces in the hand. During coordinated finger movement, the proximal interphalangeal (PIP) joint initiates flexion and extension, while the DIP joint is the first to complete its range of motion, a pattern governed by the extensor apparatus and tendon balance.

Clinical Significance

• The DIP joints are the most common site of osteoarthritis in the hand, with at least 60% of individuals over age 60 affected. Bony enlargements at the DIP joints due to osteophytes are known as Heberden's nodes.

• Common injuries include mallet finger (extensor tendon avulsion), jersey finger (FDP avulsion), and intraarticular fractures.