Last revised by Mohammad Taghi Niknejad on 19 Aug 2022

The shoulder, or shoulder joint, is the connection between the upper arm and the thorax. Comprising numerous ligamentous and muscular structures, the only actual bony articulations are the glenohumeral joint and the acromioclavicular joint (ACJ). The shoulder allows for an extensive range of motion due to the spheroid shape of the glenohumeral joint, but this (i.e. a large ball in a small socket) renders it prone to dislocation and other injuries.

The glenoid fossa of the scapula articulates with the anatomical head of the humerus as a synovial ball and socket joint. The glenoid fossa is deepened by the glenoid labrum.

The joint capsule attaches proximal to the glenoid fossa and further distally to the anatomical neck of the humerus. The capsule is looser inferiorly to allow for tightening during the abduction.

Numerous bursae are associated with the shoulder joint, which include the subacromial-subdeltoid and subcoracoid bursae.

The shoulder joint is reinforced by the rotator cuff muscles/tendons:

  • supraspinatus: from supraspinous fossa to superior facet on greater tubercle
  • infraspinatus: from infraspinous fossa to middle facet on greater tubercle
  • teres minor: from inferolateral border of the scapula to the inferior facet on the greater tubercle
  • subscapularis: from the subscapular fossa to the lesser tubercle

Arterial supply is from the branches of the scapular anastomosis but primarily from the axillary artery:

Veins with corresponding names, accompany the arteries, and drain the shoulder via a periscapular venous plexus.

Multiple articular branches are derived from several nerves (Hilton's law):

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Cases and figures

  • Fig 1: Shoulder anatomy illustrations
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  • Fig 2: Shoulder anatomy illustrations
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  • Shoulder - annotated x-rays
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