Rotator Cuff of the Shoulder

January 12, 2021 || By : Dr. MhmadFarooq || Anatomy

| Last updated on January 16, 2021

What is the rotator cuff of the shoulder?

Rotator Cuff is a group of muscles surrounding the shoulder joint.
Rotator cuff consists of 4 muscles abbreviated in the word “SITS”:
1. Supraspinatus muscle.
2. Infraspinatus muscle.
3. Teres minor muscle.
4. Subscapularis muscle.

	Supraspinatus Muscle
Origin	supraspinous fossa of scapula.
Insertion	superior facet on greater tuberosity of humerus.
Innervation	Suprascapular nerve (C4, C5 and C6) (C4,C5, C6).
Arterial Supply	Suprascapular artery.
Action	Initiates and assists deltoid in abduction of arm and acts with other rotator cuff muscles

	Infraspinatus Muscle
Origin	Infraspinous fossa of scapula.
Insertion	Middle facet on greater tuberosity of humeruss.
Innervation	Suprascapular nerve (C5 and C6) (C5, C6).
Arterial Supply	Suprascapular and circumflex scapular arteries
Action	Laterally rotate arm; helps to hold humeral head in glenoid cavity of scapula.

	Teres minor muscle
Origin	Superior part of lateral border of scapula
Insertion	Inferior facet on greater tuberosity of humerus
Innervation	Axillary nerve (C5 and C6) (C5, C6)
Arterial Supply	Subscapular and circumflex scapular arteries
Action	Laterally rotate arm; helps to hold humeral head in glenoid cavity of scapula

	Subscapularis muscle
Origin	Subscapular fossa of scapula
Insertion	Lesser tuberosity of humerus
Innervation	Upper and lower subscapular nerves (C5, C6 and C7) (C5, C6, C7)
Arterial Supply	Subscapular artery
Action	Medially rotates arm and adducts it; helps to hold humeral head in glenoid cavity of scapula

The primary function of the rotator cuff is to provide dynamic stability by balancing the force couples about the glenohumeral joint in both the coronal and transverse plane.
1. Coronal plane
  - the inferior rotator cuff (infraspinatus, teres minor, subscapularis) functions to balance the superior moment created by the deltoid
2. Transverse plane
  - the anterior cuff (subscapularis) functions to balance the posterior moment created by the posterior cuff (infraspinatus and teres minor)

Footprint of the rotator cuff means the value of space of its insertion on the humeral head.

Supraspinatus: Triangular in shape, with an average maximum medial-to-lateral length of 6.9 mm and an average maximum anteroposterior width of 12.6 mm.
Infraspinatus: Trapezoidal in shape, with an average maximum medial-to-lateral length of 10.2 mm and an average maximum anteroposterior width of 32.7 mm.
Teres minor: Triangular in shape, with an average maximum medial-to-lateral length of 29 mm and an average maximum width of 21 mm.
Subscapularis: Comma-shaped insertion, with an average maximum medial-to-lateral length of 40 mm and an average maximum width of 20 mm.