Overview

Number per hand14

Each phalanx has a base, a shaft and a head. The proximal phalanges articulate with the metacarpal heads (MCP joints) and the middle phalanges (proximal interphalangeal, PIP, joints); the middle phalanges with the distal phalanges at the distal interphalangeal (DIP) joints. The heads of proximal and middle phalanges are pulley-shaped (bicondylar), making the IP joints uniaxial hinges. The distal phalanges are short and flattened, ending in a rough ungual tuberosity (tuft) that supports the nail bed and pulp. The thumb has no middle phalanx.

The long flexor tendons insert on the bases of the middle (flexor digitorum superficialis, which splits around profundus) and distal phalanges (flexor digitorum profundus; flexor pollicis longus in the thumb). The extensor mechanism inserts by a central slip on the middle phalanx base and a terminal tendon on the distal phalanx base. Fibrous flexor sheaths with annular pulleys (A2 and A4 crucial) bind the flexor tendons to the phalanges.

Location: Fingers and thumb, distal to the metacarpals.

Parts & subdivisions

Proximal phalanges (5)
Longest; articulate with the metacarpal heads.
Middle phalanges (4)
Absent in the thumb; FDS inserts on their sides.
Distal phalanges (5)
Ungual tuberosity supports nail and pulp; FDP inserts on their bases.

Anatomy

Articulations: Metacarpophalangeal joints (condyloid) and interphalangeal joints (hinge).
Ossification: Primary centres in the shafts ≈weeks 8–12 (distal phalanges first, ossifying from the tip); a single secondary centre at the base of each phalanx (≈2–4 years), fusing ≈14–18 years.

Function

Form the skeleton of the digits for grasping and fine manipulation
Support the nails and fingertip pulp
Attachment for long flexor and extensor tendons and intrinsic muscles

Clinical significance

Mallet finger

Avulsion of the terminal extensor tendon (± bony fragment) from the base of the distal phalanx when an extended fingertip is struck (ball injury); the DIP droops and cannot be actively extended. Treated with a splint holding the DIP in extension for ≈6–8 weeks.

Jersey finger

Avulsion of flexor digitorum profundus from the distal phalanx (often ring finger) when grabbing an opponent’s jersey; inability to flex the DIP — needs early surgical repair.

Tuft fracture and subungual haematoma

Crush injuries fracture the distal tuft; a painful subungual haematoma is relieved by trephining the nail.

Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.