Serratus Posterior Superior

Origin, Insertion, Action, Innervation

Origin: Nuchal ligament and spinous processes of C7–T3 (via a broad aponeurosis)
Insertion: Superior borders of ribs 2–5 (lateral to their angles)
Action:
Primary: Elevation of ribs 2–5 during inspiration (accessory respiratory muscle)
Innervation: Ventral rami of T1–T4 (intercostal nerves)

Palpation Guide

Client position: Prone with arms at the sides.
Landmark sequence:

Serratus posterior superior lies deep to the rhomboids and trapezius in the upper interscapular region. It is not directly palpable as a separate layer.
The muscle occupies the area between the spinous processes of C7–T3 and the angles of ribs 2–5 — this corresponds to the upper medial scapular border region.
Palpation of the upper interscapular area accesses a layered complex: superficial trapezius → rhomboids → serratus posterior superior → erector spinae. Individual layers cannot be distinguished by touch.
Deep tenderness in the upper interscapular region that does not respond to rhomboid-directed treatment may involve serratus posterior superior.

Tissue feel: Not individually distinguishable. The upper interscapular region feels like a layered muscle complex. Hypertonic serratus posterior superior contributes to deep interscapular aching.
Confirmation test: No reliable confirmation test isolates serratus posterior superior. Its activation during deep inspiration is minimal and not individually palpable.
Common errors:
Attributing all upper interscapular pain to the rhomboids — serratus posterior superior lies deep to the rhomboids in the same region and contributes to the pain picture.

Trigger Point Referral

Common TrP locations: TrPs are found in the upper interscapular region, deep to the rhomboids, at approximately the T2–T3 level.
Referral pattern: Refers to the posterior shoulder, the posterior arm (overlapping triceps territory), and may extend to the dorsal forearm and hand (little finger side).
Clinical significance: The referral to the posterior shoulder and medial arm can be mistaken for C8–T1 radiculopathy or thoracic outlet syndrome. If interscapular pain radiates to the arm with negative cervical and TOS tests, consider serratus posterior superior TrPs.

Trigger point referral diagram — coming soon

Image coming soon. For visual reference, see [Serratus Posterior Superior at TriggerPoints.net](http://www.triggerpoints.net/muscle/serratus-posterior-superior).

Clinical Notes

Common conditions:

Contributor to chronic interscapular pain — the upper interscapular region contains multiple layered muscles (trapezius, rhomboids, serratus posterior superior, erector spinae), and any or all can be involved. Serratus posterior superior is the "hidden" layer that students often miss.
May be involved in upper thoracic rib dysfunction — as an elevator of ribs 2–5, hypertonicity can restrict rib depression and contribute to an inhalation rib fixation pattern.

What you'll typically find:

In clients with chronic upper interscapular pain (common in desk workers), the deep layer beneath the rhomboids is often tender and contributes to the "deep aching" quality of the complaint. When superficial rhomboid treatment provides only partial relief, serratus posterior superior is likely involved.
The muscle is rarely the primary pain generator on its own — it is typically part of a multi-layer interscapular pain complex.

Treatment effects:

Accessing the muscle requires working through the overlying rhomboids and trapezius. Sustained deep compression at the T2–T3 level, approximately midway between the spinous processes and the medial scapular border, targets this layer.
Post-treatment, the "deep" component of interscapular aching typically reduces — clients who say "the surface feels better but there's still something deep" before treatment often report complete relief after deep layer work.

Cautions:

Deep pressure in the upper interscapular region should be graduated — press through each layer progressively rather than applying maximum pressure immediately. The ribs are deep to the muscles and the lung apex is nearby.

Clinical pearl:

When treating interscapular pain, work in layers: release the superficial trapezius first, then the rhomboids, then apply deeper sustained pressure targeting serratus posterior superior and the underlying erector spinae. If you only treat the surface layers, the deep ache persists. If you go straight to deep pressure without warming the surface, the treatment is unnecessarily uncomfortable.

Assessment

Manual muscle testing:

Not individually testable. Respiratory contribution is too minor for isolated assessment.

Stretch test:

No standard clinical stretch test for serratus posterior superior. Assessment is primarily through deep palpation of the upper interscapular region.

Related special orthopedic tests:

Rib spring test — assess ribs 2–5 for inhalation fixation (rib resists depression)
Cervical and TOS screening tests — to rule out radiculopathy or vascular compression when arm referral is present

Muscle Groups

Upper interscapular layer (anatomical):

Middle trapezius (superficial)
Rhomboid major and minor
Serratus posterior superior (this article — deep)

Accessory inspiratory muscles (functional):

Serratus posterior superior (this article)
anatomy/muscles/external-intercostals
Scalenes
anatomy/muscles/diaphragm (primary)

Related Muscles

Synergists for rib elevation (inspiration):

anatomy/muscles/external-intercostals — elevate ribs during inspiration
Scalenes — elevate ribs 1–2

Antagonist:

anatomy/muscles/serratus-posterior-inferior — depresses ribs 9–12

Same region (interscapular):

Rhomboid major and minor — retract and downwardly rotate the scapula
Middle trapezius — retracts the scapula

Key Takeaways

Serratus posterior superior is the hidden deep layer in upper interscapular pain — when rhomboid treatment provides only partial relief, work deeper to address this muscle.
Treat the interscapular region in layers: trapezius first, rhomboids second, serratus posterior superior third — progressive depth produces better outcomes and less client discomfort.
The referral to the posterior arm mimics C8–T1 or TOS patterns — rule out neurological and vascular causes before attributing arm symptoms to this muscle.