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
Serratus anterior originates on the anterior surfaces of the first 8 or 9 ribs on both sides of the rib cage (Video 1) .
Serratus anterior inserts on the anterior surface of the medial border of the scapula .
Picture 1. Serratus anterior muscle origins and insertion
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 .
Picture 2. Serratus anterior actions
Actions on the ribs: Serratus anterior lifts the ribs during inhalation .
Indirect action on the upper arm: Serratus anterior helps to push your arms forward (pushing an object, making a boxing punch, push-ups or bench presses) and raising your arms forward (anteriorly), sideways (laterally) and backward (posteriorly) (Video 1) .
Video 1. Serratus anterior origin, insertion and actions (2.38 min)
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 . 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).
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
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  (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
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) . A simple massage probably does not work. Dry needling, acupuncture and injections of local anesthetics or steroids may also help relieve the pain .
Picture 3. Serratus anterior muscle pain distribution
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
- 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 or herpes zoster (pain followed by 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
Stretching exercises are intended to relieve myofascial pain in the serratus anterior.
An example of a stretching exercise [3-p.23]: Sit and reach backward 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’s 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 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:
- 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
- Serratus anterior muscle GetBodySmart
- Serratus anterior University of Washington, Department of Radiology
- Simons DG, 1987, Myofascial muscle pain due to trigger points Academyofosteopathy.org
- Jalil NA et al, 2010, Scalene Myofascial Pain Syndrome Mimicking Cervical Disc Prolapse: A Report of Two Cases PubMed Central
- Giamberardino MA et al, 2011, Myofascial pain syndromes and their evaluation ResearchGate