Flexor digitorum superficialis muscle (hand, anatomy)

Flexor digitorum superficialis is one of the forearm superficial flexor muscles of the hand and digits. It arises from three contiguous origins:

• humeral head from the:
  • common flexor origin on the medial epicondyle of the humerus
  • ulnar collateral ligament of the elbow joint
• ulnar head from its coronoid process
• radial head along anterior oblique line

The median nerve and ulnar artery pass between the thin radial part of the muscle and the thicker more lateral parts. The fused muscle divides up into four tendons through the carpal tunnel at the level of the wrist. The tendons pass distally to insert into the lateral sides of the middle phalanges of the index finger to the little finger.

Flexor digitorum superficialis is innervated by the median nerve (C7,C8).

Its action is to flex the middle phalanges of the ulnar four digits at the level of the proximal interphalangeal joints. Secondarily, it flexes the metacarpophalangeal and wrist joints.