After completing “The Shoulder Joint” section, you will be able:

  • To describe the 3 bones
  • To explain the 2 joints
  • To summarise the 4 ligaments
  • To identify the 4 rotator cuff muscles and demonstrate their action
  • To validate knowledge by completing the quiz

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The shoulder joint is made from 3 bones:

  • Humerus
  • Clavicle
  • Scapula
  • Shoulder Bones 3
    Bones of The Shoulder Joint
  • Humerus 2
  • Clavicle 1
  • Scapula2


These bones articulate to form 2 joints within the shoulder joint:

 1. Acromioclavicular (AC) joint:

  • Plane synovial (gliding) joint between the clavicle and the acromion of the scapula.

 2. Glenohumeral joint:

  • Ball and socket joint between the humeral head and the glenoid cavity of the scapula.
  • Large humeral head and shallow glenoid cavity, allows mobility however it is unstable.
  • To increase the stability, the labrum, joint capsule (ligaments) and muscles (rotator cuff, deltoid, pectoralis major) surround the glenoid cavity.


* Imagine the glenohumeral joint as a golf ball (ball) on a tee (socket). The golf ball is the humeral head, the golf tee is the glenoid cavity. Just like a golf ball on a tee, the joint is unstable which commonly leads to dislocation * 


  • The joint capsule is a lax fibrous sheath that covers the shoulder joint.
    • The ligaments (1,2,3) of the shoulder joint are thickenings of the joint capsule that provide joint capsule stability.
  • The laxity of the ligaments allows for free movement of the shoulder joint.

There are 4 main ligaments of the shoulder joint:

1. Glenohumeral ligaments:

  • Glenoid cavity → Anterior neck of the humerus.
  • Stabilises the anterior aspect of the shoulder joint.

2. Coroacohumeral ligament:

  • Base of the coracoid process → greater tubercle of the humerus.
  • Strengthens and supports anterior and superior part of the joint capsule.

3. Transverse humeral ligament:

  • Transverse across from greater tubercle of humerus → lesser tubercle of the humerus.
  • Stabilises the tendon of the long head of the bicep muscle.

4. Coracoacromial ligament:

  • Coracoid process → overlies the shoulder joint preventing superior shoulder displacement.


The rotator cuff muscles make up the main strength for the stability of the shoulder joint. There are four rotator cuff muscles, that work as a group to hold the large head of the humerus in the shallow glenoid cavity:

TIP: * Mnemonic Alert * The SITS muscles:

  • SSupraspinatus = ABDuction
  • IInfraspinatus = external rotation
  • TTeres Minor = ADDuction and external rotation
  • SSubscapularis = ADDuction and internal rotation


Moore K, Dalley A, Agur A. (2014). Clinically Oriented Anatomy. 7th ed. Philadelphia: Wolters Kluwer.

Teach Me Anatomy. (2017). The Shoulder Joint. [online]. Available at: [accessed 1 March 2017].

Tortora G, Derrickson B. (2011). Principles of Anatomy and Physiology. 13th ed. Chichester: John Wiley & Sons.


Image References

Humerus.    Clavicle.   Scapula.   Bones of The Shoulder Joint.   Shoulder Joint 1.   Shoulder Joint 2.   Shoulder Joint 3.   Ligaments 1.   Ligaments 2.   Rotator Cuff Muscles.