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Infraspinatus – Functional Anatomy

The anatomy of the infraspinatus is a bit more complicated than typically explained. A more detailed understanding is helpful for effective neuromuscular massage.

Overview of Anatomy

The infraspinatus is a flat rotator cuff muscle located in the infraspinous fossa of the scapula. Like trapezius, deltoid, and triceps, it has 3 sections:

  • The superior belly originates from the inferior edge of the spine of the scapula and inserts into the tendon of the central belly before it reaches the humerus
  • The central belly originates from the interior surface of the scapula. It thickens as it travels laterally, Eventually, until it forms a thick tendon that wraps around to the anterior greater tubercle.
  • The inferior belly originates from the caudal border of the scapula and inserts with the tendon of the teres minor.
  • The infraspinous fascia is a complex structure that covers the entire muscle. Anchoring sections of the infraspinatus is one of its many features.


Overview Attachments, Function, and Innervation

Origin: infraspinous fossa

Insertion: posterior greater tubercle of the humerus

Function: stabilize the humeral head, externally rotate the humerus

Innervation: C4-C6, Brachial Plexus, Suprascapular nerve

The idea that it originates in the infraspinous fossa and inserts on the humerus is too simplistic for effective neuromuscular massage. The most common referral occurs from the upper section, which attaches along the spine of the scapula. The referral pattern between the shoulder blades comes from the large, flat, central belly, near the medial border. Palpating for these bellies can be critical to significant release. For advanced bodyworkers, an understand of the tough, complicated structure that covers it, the infraspinous fascia, is helpful.

Also, the tendon configuration is quite different than typically explained. The central tendon is most of the attachment and continues around to the greater tubercle. Unexpectedly, the upper section attaches mostly to that tendon. Also, the lower section blends into the tendon of the teres minor.

Rotator Cuff Involvement

The infraspinatus is one of the rotator cuff muscles. These muscles stabilize the head of the humerus by strapping it tightly into the socket. The infraspinatus tendon actually wraps around the side and connects to the greater tubercle. This configuration and stabilizes the humerus from becoming anterior displaced.

Wikipedia entry for Infraspinatus

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