The serratus posterior superior is a thin, flat muscle of forced inspiration connecting the lower cervical and upper thoracic spine to the upper ribs. It is an accessory inspiratory muscle active during deep breathing and exercise, providing additional rib elevation beyond what the external intercostals and scalenes supply. In clinical practice it is more significant as a source of deep upper back pain and referred aching to the posterior shoulder than as a respiratory muscle.
| Origin | Ligamentum nuchae and spinous processes of C7 through T3 |
|---|---|
| Insertion | Upper borders of ribs 2 through 5 |
| Nerve Supply | Anterior rami of T1 through T4 intercostal nerves |
| Blood Supply | Posterior intercostal arteries |
| Actions | Elevates ribs 2 through 5 during forced inspiration |
|---|
During maximal inspiratory effort such as in aerobic exercise or respiratory failure, the serratus posterior superior is recruited alongside all accessory respiratory muscles to maximise the inspiratory volume achievable with each breath.
Serratus posterior superior trigger points produce a deep aching pain beneath the scapula and into the posterior shoulder that is reproduced by deep tissue palpation in the upper subscapular region accessible by lifting the medial scapular border. The muscle is too deep to be directly dry needled from the surface without ultrasound guidance, requiring needling through the rhomboid and trapezius layers.
Not directly palpable due to its deep position beneath the rhomboids and trapezius, but tenderness in the subscapular groove may reflect serratus posterior superior involvement alongside the rhomboids.
Deep subscapular aching from the serratus posterior superior referred beneath the scapula and to the posterior shoulder, managed with deep tissue release and subscapular dry needling.
