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Supraspinatus Muscle Anatomy

Last updated on: January 2, 2025

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The supraspinatus muscle occupies the supraspinous fossa of the scapula, situated superior to the scapular spine. A bursa separates it from the lateral quarter of the fossa.

Four of the scapulohumeral muscles (intrinsic shoulder muscles) – supraspinatus, infraspinatus, teres minor, and subscapularis (the SITS muscles) – are called rotator cuff muscles because they form a musculotendinous rotator cuff around the glenohumeral joint.

Supraspinatus Muscle Anatomy

Origin & Insertion

The supraspinatus muscle is a triangular shape muscle that originates from the medial two-thirds of the supraspinous fossa and travels laterally beneath the acromion process. The muscle converges into a robust tendon that inserts into the superior facet of the greater tubercle of the humerus, maintaining intimate relationships with the underlying glenohumeral joint capsule.

The muscle’s architecture demonstrates a pennate arrangement, with muscle fibers oriented obliquely to its central tendon. The supraspinatus tendon, approximately 2-3 cm in length, demonstrates a complex internal structure with distinct regions of differing collagen fiber orientation. The critical zone, located approximately 1 cm proximal to the insertion point, represents an area of relative hypovascularity and increased susceptibility to pathological changes.

See Also: Empty Can Test for Supraspinatus Impingement

Neurovascular Supply

The supraspinatus muscle receives its primary innervation from the suprascapular nerve, originating from the upper trunk of the brachial plexus (C5, C6). The arterial supply derives predominantly from the suprascapular artery, with additional contributions from the posterior circumflex humeral artery. Understanding this neurovascular arrangement proves crucial when evaluating potential causes of muscle dysfunction and planning surgical approaches.

Functional Significance

The supraspinatus functions as a primary initiator of shoulder abduction, particularly in the first 15-30 degrees of movement. It works synergistically with the deltoid muscle to maintain optimal glenohumeral mechanics during arm elevation. Additionally, the muscle contributes significantly to shoulder joint stability by providing a superior compressive force that helps center the humeral head within the glenoid fossa.

Origin	Supraspinous fossa of scapula
Insertion	Superior facet on greater tuberosity of humerus
Innervation	Suprascapular nerve (C4, C5 and C6)
Blood Supply	Suprascapular artery
Action	Initiates and assists deltoid in abduction of arm and acts with other rotator cuff muscles

Clinical Correlations

Understanding the precise anatomy of the supraspinatus proves essential for accurate clinical assessment and therapeutic intervention. The muscle’s position beneath the coracoacromial arch makes it susceptible to impingement syndrome, while its relatively avascular critical zone predisposes it to degenerative changes and tears. These anatomical considerations directly influence diagnostic approaches and surgical planning.

See Also: Drop Arm Test for Supraspinatus Tear

To test the supraspinatus muscle, abduction of the arm is attempted from the fully adducted position against resistance, while the muscle is palpated superior to the spine of the scapula.