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Flexor digitorum superficialisMusculus flexor digitorum superficialis

Large middle-layer forearm muscle that bends the four fingers at their middle joints and helps bend the knuckles and wrist.

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LatinMusculus flexor digitorum superficialis
Origin
  • Humeroulnar head: medial epicondyle of the humerus (common flexor tendon) and coronoid process of the ulna
  • Radial head: oblique line on the front of the upper shaft of the radius
Insertion
  • Sides of the middle phalanges of the four fingers (each tendon splits to let the flexor digitorum profundus tendon pass through)
Action
  • Flexes the fingers at the proximal interphalangeal (middle) joints
  • Flexes the fingers at the metacarpophalangeal (knuckle) joints
  • Assists wrist flexion
NerveMedian nerve (C7–T1)
GroupWrist flexors
NameLatin: the 'surface bender of the fingers (digits)'.

Palpation

  1. Client supine with the forearm palm up and relaxed.
  2. Place your fingers on the middle of the front of the forearm, between the palmaris longus and flexor carpi ulnaris lines.
  3. Hold the client's fingertips relaxed and ask them to bend one finger at a time at the middle joint; feel the belly move under the superficial flexors.
  4. Just above the wrist, feel the tendons shift between palmaris longus and flexor carpi ulnaris as the client wiggles the fingers.

Landmarks: Medial epicondyle of humerus

Flexor digitorum superficialis is the largest of the Wrist flexors. It lies under Flexor carpi radialis, Palmaris longus and Flexor carpi ulnaris, and above Flexor digitorum profundus. It is a key gripping muscle, so it is often busy in clients who type, lift or play instruments, and in massage therapists themselves.

To feel it on its own, isolate the middle finger joints: the client bends at the middle knuckle while the fingertip stays relaxed. Wikipedia notes that its slip to the little finger is commonly missing, so a weak little-finger middle joint can be a normal variation.

Techniques

  • Petrissage — Kneading strokes that compress, lift and squeeze the muscle away from the bone, working the tissue between the hands.
  • Stripping — A slow, deep, narrow glide along the length of a single muscle with the thumb, knuckle or elbow, pausing over tight bands on the way.
  • Compression — Pressing straight down into a muscle with the palm, fist or forearm, holding briefly, then releasing and moving on.
  • Trigger point pressure release — Sustained thumb or finger pressure on a tender spot within a taut band of muscle, held until the client reports the discomfort easing, then slowly released.
  • Passive stretching — The therapist gently moves a relaxed limb to lengthen a muscle to a point of mild stretch and holds it there, with no effort from the client.

Works with

  • Flexor digitorum profundus — Deep forearm muscle lying on the ulna that bends the fingertips and is the only muscle able to flex the end joints of the four fingers.

Opposes

  • Extensor digitorum — Muscle in the middle of the back of the forearm whose four tendons straighten the fingers and help extend the wrist.

Same group

  • Flexor carpi radialis — Superficial forearm muscle that runs from the medial epicondyle to the index and middle finger metacarpals, bending the wrist and tilting it towards the thumb.
  • Flexor carpi ulnaris — Superficial muscle along the inner (little-finger) border of the forearm that bends the wrist and tilts it towards the little finger.
  • Flexor digitorum profundus — Deep forearm muscle lying on the ulna that bends the fingertips and is the only muscle able to flex the end joints of the four fingers.
  • Palmaris longus — Small, slender forearm muscle with a long tendon that tightens the fascia of the palm and weakly bends the wrist; missing in some people.

Sources

  1. Wikipedia: Flexor digitorum superficialis muscle
  2. Gray's Anatomy of the Human Body (1918), Myology 7e: The Muscles and Fasciae of the Forearm (Public domain. Used for the heads of origin and nerve roots (C7, C8, T1, as in Wikipedia).)