Middle Trapezius

Origin, Insertion, Action, Innervation

Origin: Spinous processes of C7–T3 (some sources extend to T5), supraspinous ligaments
Insertion: Medial margin of the acromion, superior lip of the spine of the scapula
Action:
Primary: Retraction (adduction) of the scapula
Stabilization of the scapula against the thoracic wall during arm movements
Innervation: Spinal accessory nerve (CN XI, motor) and ventral rami of C3–C4 (proprioception and pain)

Palpation Guide

Client position: Prone with the arm hanging off the table, or seated. Prone is preferred because the scapula rests in a neutral position.
Landmark sequence:

Locate the spine of the scapula by tracing from the acromion posteromedially. The spine is a prominent bony ridge.
Place your fingers just above the spine of the scapula, between the scapular spine and the spinous processes of the upper thoracic vertebrae. The middle trapezius fibers run horizontally in this space.
Trace the fibers medially toward the spinous processes of C7–T3 and laterally toward the acromion and scapular spine.
Note the distinction from upper trapezius (fibers above this level run inferolaterally) and lower trapezius (fibers below run superolaterally).

Tissue feel: Thinner than upper trapezius. In a healthy state, feels like a flat sheet of muscle over the rhomboids beneath. In an inhibited state (common), feels soft and atrophic compared to a hypertonic upper trapezius above it.
Confirmation test: Ask the client to retract the scapula (squeeze shoulder blades together) while you resist by pushing the shoulder forward. You will feel the horizontal fibers contract under your hand.
Common errors:
Confusing middle trapezius with rhomboids — rhomboids lie deep to middle trapezius and retract with downward rotation. Resisted retraction with the arm at the side activates both; resisted horizontal abduction at 90 degrees isolates middle trapezius more effectively.
Missing the transition zone between upper and middle trapezius at the level of the acromion — upper fibers run inferolaterally, middle fibers run horizontally.
Palpating too far inferiorly and landing on lower trapezius — the division occurs approximately at T3–T4, where fibers shift from horizontal to superomedial.

Trigger Point Referral

Common TrP locations: A primary TrP is found midway between the thoracic spinous processes and the medial border of the scapula, at approximately the T3–T4 level. A secondary TrP sits closer to the acromion along the scapular spine.
Referral pattern: The primary TrP refers medially toward the spinous processes, producing a burning or aching sensation along the upper thoracic spine. The secondary TrP may refer toward the acromion.
Clinical significance: The interscapular burning that desk workers describe as "pain between my shoulder blades" is frequently middle trapezius TrPs, not thoracic spine pathology. Check middle trapezius and rhomboid TrPs before investigating facet or disc involvement.

Trigger point referral diagram — coming soon

Image coming soon. For visual reference, see [Trapezius at TriggerPoints.net](http://www.triggerpoints.net/muscle/trapezius).

Clinical Notes

Innervation significance:

Shares CN XI innervation with upper trapezius and SCM. Despite this shared nerve supply, middle trapezius is typically inhibited while upper trapezius is hypertonic — the imbalance is driven by postural loading patterns, not nerve dysfunction.

Common conditions:

One of the primary "weak" muscles in conditions/upper-crossed-syndrome — becomes lengthened and inhibited as the scapulae protract. Reciprocally inhibited by hypertonic anatomy/muscles/pectoralis-major and anatomy/muscles/pectoralis-minor.
Weakness contributes to conditions/subacromial-impingement — without adequate scapular retraction, the scapula fails to posteriorly tilt during overhead movements, narrowing the subacromial space.
Involved in chronic interscapular pain presentations, which students often misattribute to thoracic spine dysfunction.

What you'll typically find:

In clients with rounded-shoulder posture, middle trapezius is lengthened and weak bilaterally. It often feels thin and soft compared to the dense, hypertonic upper trapezius above it. TrPs in the belly produce the classic interscapular burning complaint.
Asymmetry is common in clients with dominant-side protraction patterns (e.g., computer mouse users).

Treatment effects:

TrPs respond to sustained compression and cross-fiber techniques along the horizontal fibers. Because the muscle is often inhibited rather than hypertonic, treatment should include activation exercises (scapular retraction, prone Y-raises) in addition to TrP release.
Post-treatment, clients often report reduced interscapular burning and a sense of the shoulders sitting further back.

Cautions:

The thoracic spinous processes are directly beneath the medial attachment — avoid excessive pressure directed anteriorly toward the spine, particularly in clients with osteoporosis.
In clients with significant scapular winging, the medial border of the scapula may be prominent — work carefully along this edge.

Postural significance:

Middle trapezius is the primary antagonist to scapular protraction. In upper crossed syndrome, it is reciprocally inhibited by shortened pectorals. Strengthening middle trapezius (along with lower trapezius) is essential for restoring scapular position. Without active retraining, manual therapy alone will not correct protracted scapulae.

Clinical pearl:

If a client presents with persistent interscapular pain that does not respond to middle trapezius TrP work, check anatomy/muscles/serratus-anterior — a hypertonic serratus anterior can maintain scapular protraction and perpetuate middle trapezius strain. Also assess pectoralis minor length — if the pecs are not addressed, middle trapezius cannot hold its corrected position.

Assessment

Manual muscle testing:

Scapular retraction (horizontal abduction at 90°): Client prone with the arm hanging off the table, then horizontally abducting to 90° with the elbow extended and thumb pointing toward the ceiling (external rotation). Apply downward resistance on the forearm. This position biases middle trapezius over rhomboids. Grade bilaterally and compare.

Stretch test:

Scapular protraction stretch: Client seated. Reach the arm across the body (horizontal adduction) while stabilizing the thoracic spine. Compare bilaterally for restriction. Limited horizontal adduction suggests a shortened middle trapezius.

Related special orthopedic tests:

Scapular dyskinesis observation — altered scapular movement patterns during arm elevation suggest middle trapezius weakness
Wall push-up test — scapular winging during push-up indicates serratus anterior and/or middle/lower trapezius weakness

Muscle Groups

Trapezius group (anatomical — three divisions of the same muscle):

Scapular retractors (functional):

Middle trapezius (this article)
anatomy/muscles/rhomboids

Upper crossed syndrome — "weak" group (clinical):

Middle trapezius (this article)
anatomy/muscles/lower-trapezius
anatomy/muscles/serratus-anterior
Deep cervical flexors

Spinal accessory nerve group (innervation):

Related Muscles

Synergists for scapular retraction:

anatomy/muscles/rhomboids — retract and downwardly rotate the scapula; lie deep to middle trapezius

Antagonists:

anatomy/muscles/serratus-anterior — primary scapular protractor
anatomy/muscles/pectoralis-minor — tilts scapula anteriorly and protracts

Same innervation (spinal accessory nerve):

anatomy/muscles/upper-trapezius — shares CN XI; typically hypertonic when middle trapezius is inhibited
anatomy/muscles/lower-trapezius — shares CN XI; also typically weak in upper crossed syndrome

Key Takeaways

Typically inhibited (not hypertonic) in upper crossed syndrome — strengthening is as important as releasing its antagonists.
Interscapular burning between the shoulder blades is most often middle trapezius and rhomboid TrPs, not thoracic spine pathology.
Release alone is insufficient — if the pectorals are not lengthened and scapular retractors are not retrained, the pattern returns.