Upper limb

Flexor Digitorum Superficialis (radial head)

Musculus flexor digitorum superficialis (caput radiale)

Origin

Anterior border (oblique line) of the radius

Insertion

Sides of the middle phalanges of fingers 2 through 5 (together with the humeroulnar head)

Function

Flexes the PIP joints of fingers 2–5

Innervation

Median nerve, C7–T1

Movement & chain

Together with the humeroulnar head forms a single functional muscle that can be driven separately per finger: tested by isolating each finger while the others are held extended.

Palpation

Cannot be distinguished from the humeroulnar head on palpation; together palpable as the taut tendon mass in the mid-volar wrist.

Clinical

Tendon injury (for example from a hyperextension trauma) leads to loss of PIP flexion of the affected finger, while DIP flexion may be preserved via flexor digitorum profundus.

Segmental innervation

Median nerve, C7–T1.

In clinical practice

The clinical FDS test (flexing each finger separately while holding the other fingers extended) is used to distinguish tendon injuries of the superficial versus deep finger flexors.

Region in the model

Upper limb