Upper limb

Flexor Digitorum Superficialis (humeroulnar head)

Musculus flexor digitorum superficialis (caput humeroulnare)

Origin

Medial epicondyle of the humerus, ulnar collateral ligament, and coronoid process of the ulna

Insertion

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

Function

Flexes the PIP joints of fingers 2–5; assists flexion of the MCP joints and wrist

Innervation

Median nerve, C7–T1

Movement & chain

Works independently per finger, unlike the deep finger flexor, which acts more as a whole. Important for graded gripping movements such as typing.

Palpation

The tendons are easily palpated on the volar side of the wrist between flexor carpi radialis and flexor carpi ulnaris.

Clinical

Together with the radial head, this muscle forms the bulk of the superficial muscle compartment; a 'jersey finger' actually involves the deep flexor, while a limitation of PIP flexion is more often associated with this muscle.

Segmental innervation

Median nerve, C7–T1.

In clinical practice

Function per finger is tested by holding the remaining fingers in full extension and having the patient flex only the PIP joint of the finger being tested; this isolates the superficial flexor from the deep finger flexor.

Region in the model

Upper limb