Finger Anatomy

The margins of the extensor expansion over the dorsal aspect of the proximal phalanges and PIPJs are reinforced by tendons of the intrinsic muscles of the fingers.

The dorsal and palmar interossei arise from the sides and fronts of the metacarpals respectively.

The lumbricals are distinctive as they take origin from (and are inserted into) tendons; they arise from the four profundus tendons and run on the radial side of the MCPJ to join the extensor expansion.

The palmar intrinsic muscles all flex the MCPJ and extend the IPJ. In addition, the three palmar interossei adduct the fingers (relative to the middle finger), and the four dorsal interossei abduct the fingers.

The little finger is assisted by the abductor digiti minimi (ADM) in abduction. The ADM, together with the opponens digiti minimi and the flexor digiti minimi, form the hypothenar eminence.