Proximal phalanx of middle finger: anatomy, location and function

What it is

The longest of the three phalanges of the middle finger (third digit), nearest the palm.

Location

Its base articulates with the head of the metacarpal at the metacarpophalangeal joint; its head articulates with the middle phalanx at the proximal interphalangeal joint.

Function

Forms the base of the finger and allows flexion, extension, abduction and adduction at the knuckle.

Body system

Skeletal · paired (left and right)

FMA ID

FMA71908 (Foundational Model of Anatomy)

Key facts

• The second and third dorsal interossei insert on either side of its base, so the middle finger can be moved to both sides but has no palmar interosseous.
• Its head forms the proximal interphalangeal joint, a hinge joint stabilised by collateral ligaments and the palmar plate.
• The extensor expansion (dorsal hood) wraps around it, receiving the lumbrical on its radial side.

Clinical relevance

Fractures of the proximal phalanx usually angulate with the apex toward the palm because of the pull of the interossei and extensor hood; rotation must be corrected so the middle finger does not cross its neighbours when making a fist.

The nearest named structures in the 3D model, measured from the centre of each part:

• Proximal phalanx of ring finger · skeletal
• Proximal phalanx of index finger · skeletal
• Lumbricals of hand · muscular
• Middle phalanx of ring finger · skeletal
• Middle phalanx of middle finger · skeletal
• Palmar interossei of hand · muscular
• Proximal phalanx of little finger · skeletal
• Middle phalanx of index finger · skeletal
• Middle phalanx of little finger · skeletal
• Dorsal interossei of hand · muscular