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Serratus anterior
The muscle between the shoulder blade and the ribs that lets you reach forward and lets the arm go fully overhead.
Latin name: Musculus serratus anterior. In plain English, the finger-like muscle on the ribs that pins the shoulder blade down. It is filed here under shoulder and shoulder blade.
Reference information, not a diagnosis. Where a symptom is described below, it is there so you can describe your own more precisely to a clinician — not so you can name what you have.
Where it is
Serratus anterior is one of the few muscles you can see clearly on a lean person: the toothed slips over the side of the rib cage, below the armpit, that give it its name. It passes behind the shoulder blade and attaches to the surface facing the ribs, so it works by pulling the blade forward around the curve of the chest wall.
Its nerve, the long thoracic, runs down the outside of the rib cage in an exposed position with no muscle covering it. That exposure is why it can be injured by a blow to the side of the chest, by carrying a heavy pack, or during chest surgery, and why the resulting winged shoulder blade is such a recognisable sign.
| Feature | Detail |
|---|---|
| Origin | Outer surfaces of the upper eight or nine ribs |
| Insertion | Costal surface of the medial border of the scapula, with the strongest slips at the inferior angle |
| Nerve | Long thoracic nerve (C5-C7) |
| Main actions | Protraction of the shoulder blade, upward rotation of the socket, and holding the blade flat against the rib cage |
What it does
Two jobs. First, protraction: reaching, punching, pushing, and the last few centimetres of a push-up when the shoulder blades slide apart. Second, and more important, upward rotation. For the arm to rise fully overhead the socket must tilt to face upward, and serratus anterior working with the upper and lower trapezius produces that rotation. Without it the arm jams at shoulder height.
It is also a postural anchor. Holding the shoulder blade flat against the ribs while the arm works out in front of the body is continuous serratus work. When it fails — usually because of long thoracic nerve injury — the medial border of the blade lifts away from the chest and stands out like a wing, most obviously when pushing against a wall.
Exercises that load it
| Exercise | Category | Muscles the exercise library lists |
|---|---|---|
| Push-ups | Strength | Chest, triceps, front shoulder, core |
| Plank | Core | Deep core, shoulders, glutes |
| Overhead press | Strength | Shoulders, triceps, core |
| Dips | Strength | Triceps, chest, front shoulder |
The classic loading is the top of a push-up: after the elbows lock, keep pushing so the shoulder blades slide apart around the rib cage. Plank positions load it isometrically for the same reason — the blades are being held forward and flat against the ribs by nothing else. Overhead pressing loads it through the upward rotation it has to produce for the arm to finish the movement.
How it is lengthened
Serratus anterior is rarely stretched deliberately and rarely needs to be. Squeezing the shoulder blades together lengthens it, and any doorway chest opener does so incidentally. If reaching overhead is limited, the useful question is usually whether the blade rotates, not whether this muscle is short.
When it goes wrong
| Problem | What it typically feels like | Usual setting |
|---|---|---|
| Scapular winging | The inner edge of the shoulder blade lifts off the ribs, most visible pressing against a wall, with weak overhead reach | Long thoracic nerve injury after a blow, a heavy pack, a viral illness or chest surgery |
| Shoulder blade fatigue pain | A burning ache under and around the shoulder blade during sustained reaching or pressing work | Repeated overhead or forward-reaching work without enough recovery |
| Rib-cage-side muscle strain | A sharp catch over the side of the ribs on deep breathing or twisting | A hard rotational effort — throwing, a racquet sport, a heavy awkward lift |
A shoulder blade that visibly sticks out from the chest wall, or a shoulder that cannot be raised fully overhead, is a nerve sign and needs a clinical assessment, not an exercise programme found online.
Nothing on this page is a treatment plan. If a problem is limiting what you do, is not improving, or is getting worse, the right next step is an assessment by a doctor or a physiotherapist who can examine you.
Sources: descriptive anatomy from Gray's Anatomy of the Human Body, 20th US edition (1918), which is in the public domain; Latin names follow Terminologia Anatomica, published by the Federative International Programme for Anatomical Terminology. Nerve root levels are the conventional ranges taught from those sources and vary between individuals and between textbooks. Exercise cross-links use the TempoLife exercise library. Checked 2026-09-06.
Frequently asked questions
What causes a winged shoulder blade?
Most commonly weakness or paralysis of serratus anterior from injury to the long thoracic nerve. There is also a different pattern, from trapezius weakness through the accessory nerve, which wings the blade in the opposite direction. Telling them apart is an examination, not a photograph.
How do I know if my serratus anterior is working?
The practical check is whether your arms go fully overhead with the trunk upright, and whether the shoulder blades stay flat against the ribs when you push against a wall. Anything more specific needs someone watching you move.
Is serratus anterior a core muscle?
It is not part of the abdominal wall, but it does connect the arm to the rib cage, so it is doing genuine trunk work in every plank, push-up and overhead carry. The label matters less than the fact that it works hard in those positions.
Nearby in this reference
Deltoid
The cap of the shoulder
Rotator cuff
The four small muscles that hold the shoulder in its socket
Trapezius
The big diamond across the upper back and neck
Rhomboids
The straps that pull the shoulder blades together
Biceps brachii
The two-headed muscle at the front of the upper arm
Triceps brachii
The three-headed muscle at the back of the upper arm
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