Muscles Acting at the Shoulder Joint

bones of the forearm deltoid infraspinatus latissimus dorsi pectoralis major rotator cuff subscapularis supraspinatus teres major teres minor

Muscles of the shoulder joint Physiotherapy Solihull Simon Evans

Muscles of the Shoulder

  • Functionally divided into 
    • Superficial Anterior Muscles - Pectoralis major
    • Superficial Posterior Muscles - Latissimus dorsi, teres major
    • Lateral Muscles - deltoid
    • Rotator Cuff - deep stabilising group

Pectoralis Major (Superficial Anterior Muscles)

  • Large powerful muscle covering the anterior chest wall
  • Arises from 2 heads
    • Clavicular head – anterior border of medial ½ of clavicle
    • Sternal head – body of sternum, costal cartilages of upper 6 ribs, aponeurosis of the external abdominal oblique (rectus sheath)
  • 2 lamina cross to form flat tendon which inserts into the lateral lip of intertubercular sulcus
  • A: Adduction and medial rotation of glenohumeral joint. Clavicular head will produce flexion  of the shoulder. Sternal head will extend form a flexed position
  • NS: Medial & lateral pectoral nerves (C5-T1) 

Latissimus Dorsi (Superficial Posterior Muscles)

  • Large powerful muscle that unites the pelvic and pectoral girdles
  • From thoracolumbar fascia, spinous processes of T6-L5, outer lip of posterior 1/3 of iliac crest
  • To floor of intertubercular sulcus (may attach to lower 3 or 4 ribs and occasionally to inferior angle of the scapula)
  • A: Extension, adduction and medial rotation of shoulder – often termed the climbing muscle due to its action
  • NS: Thoracodorsal nerve (C6, 7 & 8) 

Teres Major

  • Short powerful muscle on posterior aspect of shoulder
  • Arises from the posterior aspect of the inferior angle and lower part of lateral border
  • Passes though the axilla forming the posterior wall to insert onto the medial lip of the intertubercular sulcus
  • A: medial rotation, extension and adduction
  • NS: Lower subscapular nerve (C6,7)


  • Thick powerful muscle forming the contour of the shoulder
  • Divided into 3 sections
    • Anterior fibres – from anterior order of lateral 1/3 of clavicle
    • Middle fibres from lateral border of acromion process
    • Posterior fibres from the inferior border of the spine of the scapula and fascia covering infraspinatus
  • All 3 heads converge to form a common tendon which inserts into the deltoid tuberosity on the humerus
  • Actions
    • Ant – flexion/medial rotation
    • Middle – abduction
    • Posterior – extension/lateral rotation
  • NS: Axillary nerve (C5, 6)

The Rotator Cuff

  • Group of 4 muscles that acts as ‘musculotendinous ligaments’ of the shoulder
  • Act as fingers gripping the head of humerus holding it into the glenoid fossa during movements
  • Key stabilisers of the glenohumeral joint

1. Supraspinatus

  • Most superior of rotator cuff - provides superior support to GHJ
  • Arises from the medial 2/3s of the supraspinous fossa
  • Passes laterally under the acromion process (separated by subacromial burse) to insert into the superior facet on the greater tubercle
  • A: Abduction of the GHJ
  • NS: Suprascapular nerve (C4,5 & 6)

2. Infraspinatus

  • Forms posterior element of cuff with teres minor
  • Arises from medial 2/3s of infraspinous fossa
  • Passes under posterior acromial angle to insert into the middle facet on the greater tubercle – separated from scapula neck by infraspinatus bursa
  • A: Lateral rotation of GHJ
  • NS: Suprascapular nerve (C4,5 & 6)

3. Teres Minor

  • Assists infraspinatus in providing posterior stability to GHJ
  • Arises from the upper 2/3s of lateral border of the scapular
  • Inserts into the lower facet of the greater tubercle
  • A: Adduction and lateral rotation - prevents upward subluxation of humerus
  • NS: Axillary nerve (C(4),5,6)

4. Subscapularis

  • Stabilises the anterior aspect of the GHJ
  • Lies between the scapula and thoracic cage
  • Arises from the medial 2/3s of the subscapular fossa
  • Inserts into the lesser tubercle - separated fthe the anterior GHJ by the subscapualr bursa
  • A: Medial rotation and adduction of GHJ
  • NS: Subscapular nerve (C5,6,7)

Bones of the Forearm

  • Radius (lateral) and ulna (medial)
  • Both classified as long bones

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