Serratus Anterior Muscle Origin, Insertion, Function

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Published: June 29, 2016
Last reviewed: December 9, 2016

What is serratus anterior?

Serratus anterior is a muscle that runs from the side of the rib cage to the front surface of the scapula on each side.

Serratus anterior word origin: from the Latin serrare = to saw (referring to its shape); anterior = on the front of the body

Synonyms: big swing muscle, boxer’s muscle, serratus magnus

Origin

Serratus anterior originates on the anterior surfaces of the first 8 or 9 ribs on both sides of the rib cage (Video 1) [1].

Insertion

Serratus anterior inserts on the anterior surface of the medial border of the scapula [1].

Serratus anterior muscle

Picture 1. Serratus anterior muscle origins and insertion
(free image use)

Actions

Actions on the scapula: Serratus anterior holds the scapula close to the rib cage and thus stabilizes it. During a forward movement of the upper arm, like during a boxing punch, it abducts (moves laterally, away from the spine) and protracts it (brings it forward). It also rotates the scapula upwards while abducting an arm or lifting weight over the head [1].

Serratus anterior actions

Picture 2. Serratus anterior actions
(free image use)

Actions on the ribs: Serratus anterior lifts the ribs during inhalation [1].

Indirect action on the upper arm: Serratus anterior helps pushing your arms forward (pushing an object, making a boxing punch, push-ups or bench presses) and raising your arms forward (anteriorly), sideways (laterally) and backwards (posteriorly) (Video 1) [1].


Video 1. Serratus anterior origin, insertion and actions (2.38 min)

Innervation

Serratus anterior is innervated by the long thoracic nerve, which is a branch of the brachial plexus; the nerve fibers arise from the spinal roots C5-C7 [2]. The nerve travels vertically down from the armpit along the middle axillary line. The nerve can be damaged by a direct hit to the side of the chest or during surgical removal of the lymph nodes in the armpit — this results in a winged scapula (the medial border of the scapula sticking out).

Bursae

Bursa is a fluid-filled sac that prevents the friction between the muscles or between the muscles and bones or joints. Serratus anterior lies under the subscapularis muscle from which it is separated by the subscapularis (supraserratus) bursa. It is separated from the ribs by the scapulothoracic (infraserratus) bursa.

Related anatomy: shoulder muscles

Serratus Anterior Muscle Pain Syndrome

Causes

Arm swinging during sprints, running, swimming, weightlifting, tennis, push-ups, chin-ups, repeated lifting of heavy objects with the extended arms, hyperventilation or prolonged hard cough can cause myofascial pain in the serratus anterior muscles.

Symptoms and Signs

  • Pain between and below the shoulder blades, on one or both sides of the chest, especially below the armpits [4] (Picture 3)
  • Sharp pain on one or both sides of the chest triggered by deep breathing, coughing, twisting your upper body or lifting the arms
  • Tenderness below the armpits; applying pressure on the muscle knots that act as trigger points at the level of the 5th to 7th rib can trigger pain that can radiate down the inner side of the arm down to the 4th and 5th finger
  • Difficulty reaching behind the back or above the head

Treatment

Mild serratus anterior pain should improve within several days of avoiding the activities that caused the pain.

Note that serratus anterior pain is usually caused by a repeated overuse and not by an actual injury, such as muscle strain, pull or tear. This means that while the rest from the causing activities can help, stretching exercises, unlike in injuries, may also help relieve the pain.

A physiotherapist may find muscle knots or taut bands at the side of the chest below the armpit, cool the area with a vapocoolant spray (to decrease tenderness) and apply pressure on them and eventually release them (myofascial pain release technique) [5]. A simple massage probably does not work. Dry needling, acupuncture and injections of local anesthetics or steroids may also help relieve the pain [5].

Serratus Anterior Muscle Pain image

Picture 3. Serratus anterior muscle pain distribution

Differential Diagnosis

Other conditions that can cause pain on the side of the chest, below the shoulder blade or down the inner side of the arm:

  • Side stitch
  • Trapped wind
  • Pleurisy
  • Contusion or rib fracture after a fall or blunt trauma
  • Kidney disease (pain in the middle back at the bottom of rib cage)
  • Enlarged spleen or other cause of spleen pain (on the left side)
  • Gallbladder disease (on the right side)
  • Shingles (with or without rash)
  • Coronary heart disease (pain behind the breastbone, in the left shoulder blade and arm)
  • Adhesions after abdominal surgery
  • Thoracic outlet syndrome (a compression of the brachial plexus)
  • Pneumothorax or adhesions in the pleural cavity after its treatment by pleurodesis

Exercises

Stretching Exercises

Stretching exercises are intended to relieve myofascial pain in the serratus anterior.

Example of a stretching exercise [3-p.23]: Sit and reach backwards with your arm and shoulder on the affected side. Then reach back with your unaffected arm and grab the affected arm at the elbow and pull to assist the stretch. Repeat several times at the time few times a day.

Wall presses. Stand facing a wall, arm distance length from it and place the hands on it at the shoulder height. Push your upper body toward the wall without bending the elbows and then go back to the original position (Video 2).


Video 2. Wall presses (1.04 min)

Strengthening Exercises

Strengthening exercise are intended to increase the strength of the serratus anterior muscles in sports, like swimming or tennis, and to reduce the risk of injuries. Examples:

  • Push-ups
  • Plank with only your toes and forearms touching the floor
  • While lying on the back, lift your arms with the hands pointing toward the ceiling and then reach even further up using your shoulder blade muscles (later you can use dumbbells to increase resistance)
  • Punching a boxing bag
  • Pulling a rope

3 thoughts on “Serratus Anterior Muscle Origin, Insertion, Function”

  1. Juliette Louise Regan says:

    I have excrutiating upper left back pain in what seems like cramps! Its starts there and then goes through to the chest! My neck and shoulder Doctor told me my neck muscles are far too tight and pushing on my neck but having a knock on affect in the top left muscle are around my shoulder blades. Please help!!

  2. Kris says:

    I have a shrill and very sharp 1 – 2 seconds pain one palm length below neck on the left shoulder rear blade. The pain is so acute that for that moment I have to let go any work I am doing. It has been there for a month now. It disappeared for last 10 days but is reoccurred since last 2 days. Its frequency is 2 -3 times in a day. Now even when the pain attack is over a slight burning sensation persists.

    1. Jan Modric says:

      I don’t know but it sounds it could be a strained/ruptured muscle or even a broken shoulder blade or rib. I suggest you to visit a doctor.

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