Rotator cuff of the shoulder

Consists of four muscles, critical in the stabilisation of the glenohumeral joint. The rotator cuff muscles compress the humeral head against the concave surface of the glenoid and labrum, as well as provide force coupling during shoulder movements to maintain the central position of the humeral head within the glenoid fossa. Each muscle also has an action on the shoulder joint when functioning in isolation.

  • Supraspinatus
  • Infraspinatus
  • Teres minor
  • Subscapularis

Supraspinatus

Origin/Insertion

  • Bipennate muscle that arises from medial three quarters of supraspinous fossa and superior surface of the spine of the scapula
  • Tendon develops deep to the muscle as it crosses the superior part of the capsule and then blends into it
  • Inserts onto the smooth facet on the upper part of the greater tuberosity

Action

  • Important in initiation of abduction of the shoulder joint
  • As the supraspinatus pulls the greater tubercle upward, the articular surface of the humerus slides inferiorly on the glenoid

Nerve supply

  • Suprascapular nerve (C5, 6)
    • From upper trunk of brachial plexus
    • Passes beneath superficial transverse scapular ligament within suprascapular notch

Blood supply

  • Suprascapular artery
    • Branch of thyrocervical trunk (major branch of the subclavian artery)
    • Enters posterior scapular region via the suprascapular notch

Infraspinatus

Origin/Insertion

  • Multipennate muscle arising from medial three quarters of infraspinous fossa
  • Fibres converge to slide over bare area of scapula at the lateral angle, with a bursa lying between the muscle and bone
  • Tendon replaces muscle as it blends with the capsule of the shoulder
  • Inserts onto the smooth area on the central facet of the greater tuberosity, between supraspinatus (above) and teres minor (below)

Action

  • External rotation of the humerus
  • During abduction…

Nerve supply

  • Suprascapular nerve (C5,6)
    • After giving branches to supraspinatus (as above), passes around the lateral border of the scapular spine and enters the infraspinous fossa

Blood supply

  • Suprascapular artery
    • Branch of thyrocervical trunk (major branch of the subclavian artery)
    • Enters posterior scapular region via the suprascapular notch

Teres minor

Origin/Insertion

  • Arises from elongated oval area at axillary border of scapula
  • Passes upwards and laterally, along the inferolateral border of infraspinatus
  • Passes posterior to the long head of triceps
  • Inserts to the lower facet of the greater tuberosity

Action

  • Acts as a force couple with teres major to inferiorly glide the head of the humerus on the glenoid during abduction
  • External rotation of the humerus
  • Can act as a weak adductor

Nerve supply

  • Posterior branch of the axillary nerve (C5, 6)
    • From the posterior cord of the brachial plexus

Blood supply

  • Posterior circumflex artery
    • Originating from the third part of the axillary artery
    • Enters the posterior scapular region through the quadrangular space (with the axillary nerve)

Subscapularis

Origin/Insertion

  • Arises from medial four-fifths of costal surface of scapula
  • Multipennate muscle converges over lateral angle of scapula with musculotendinous fibres separated from bone by the subscapularis bursa
  • Tendon insertion fuses with the capsule of the shoulder joint and attaches to the lesser tuberosity and medial lip of intertubercular groove

Action

  • Acting as a prime mover, it is a internal rotator of the humerus

Nerve supply

  • Upper and lower subscapular nerves (C5,6)
    • From posterior cord of brachial plexus

Blood supply

  • Subscapular artery
    • Largest brach of the axillary artery, originating from the third part of the axillary artery

References

Last, R. and McMinn, R., 1994. Last’s Anatomy. 9th ed. Edinburgh: Churchill

Ecklund, Kier, Lee, Thay, Tibone, James, Gupta, Ranjan. Rotator Cuff Tear Arthropathy. J Am Acad Orthop Surg. 2007;15(6):340-349

Maruvada S, Madrazo-Ibarra A, Varacallo M. Anatomy, Rotator Cuff. [Updated 2021 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441844/

Author contributions

Christopher Mackenzie, Intern, Western Health 2022