MedCourseFinder

Structure

Rotator cuff

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The rotator cuff comprises four scapular muscles, supraspinatus, infraspinatus, teres minor and subscapularis (SITS), whose tendons fuse with the glenohumeral capsule. They centre the humeral head in the glenoid and are the dynamic stabilisers of the shoulder.

Terminologia Anatomica (Latin): Musculi supraspinatus, infraspinatus, teres minor et subscapularis · Open in the 3D atlas

Location

Supraspinatus, infraspinatus and teres minor lie on the posterior scapula and insert on the greater tubercle of the humerus (superior, middle, inferior facets); subscapularis lies on the anterior scapular surface and inserts on the lesser tubercle. The supraspinatus tendon passes beneath the acromion and the coracoacromial ligament.

Structure

Supraspinatus originates in the supraspinous fossa, infraspinatus in the infraspinous fossa, teres minor on the lateral scapular border and subscapularis in the subscapular fossa. The tendons blend into a continuous cuff around the humeral head, with a relatively hypovascular zone in the supraspinatus tendon near its insertion (the critical zone). The subacromial bursa lies between the cuff and the acromion.

Blood supply

The suprascapular, circumflex scapular and posterior circumflex humeral arteries supply the posterior muscles; the subscapular artery and branches of the suprascapular and anterior circumflex humeral arteries supply subscapularis.

Innervation

Suprascapular nerve (C5-C6): supraspinatus and infraspinatus. Axillary nerve (C5-C6): teres minor. Upper and lower subscapular nerves (C5-C7): subscapularis.

Function

Supraspinatus initiates abduction (first 15 degrees, approximate) and compresses the head in the glenoid; infraspinatus and teres minor externally rotate; subscapularis internally rotates. Together they resist upward pull by the deltoid and hold the humeral head in the socket.

Clinical correlations

Supraspinatus is the most commonly torn cuff tendon, producing a painful arc of abduction, weakness and a positive drop-arm sign; chronic subacromial impingement and calcific tendinitis are related. Teres minor and infraspinatus tears reduce external rotation; subscapularis tears reduce internal rotation (lift-off test). Suprascapular nerve entrapment at the notch causes infraspinatus and supraspinatus wasting.

Common exam points

  • SITS: supraspinatus, infraspinatus, teres minor, subscapularis; all insert on the humeral tubercles (greater: first three; lesser: subscapularis).
  • Supraspinatus: abduction initiation, suprascapular nerve, most frequently torn; empty can/Jobe test.
  • Infraspinatus and teres minor: lateral rotation; teres minor is supplied by the axillary nerve.
  • Subscapularis: medial rotation, upper and lower subscapular nerves; lift-off and belly-press tests.
  • Painful arc between about 60 and 120 degrees of abduction suggests subacromial impingement.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Netter FH. Atlas of Human Anatomy. Elsevier — Tier 3 (textbook)

References are listed only where the article cites them. See the sources page for the full policy. How sources are chosen and credited

Back to the index