Posterosuperior impingement of the shoulder

Last revised by Ian Bickle on 16 Dec 2021

Posterosuperior impingement, also known as internal impingement, is a relatively uncommon form of shoulder impingement primarily involving the infraspinatus tendon and the posterosuperior glenoid labrum. It occurs when the shoulder is abducted and externally rotated (ABER position).

Patients present with posterior shoulder pain and instability. It almost exclusively occurs in athletes who repetitively place their shoulder into extreme abduction and external rotation such as throwers, swimmers, volleyball players and tennis players. 

An extreme abduction and external rotation (ABER) position results in repeated impingement of the infraspinatus tendon and the posterior portion of the supraspinatus tendon between the head of the humerus and the posterior superior rim of the glenoid. There is resulting tendon degeneration, reactive humeral head cysts, and glenoid labrum degeneration.  

Features include 4,6:

  • greater tuberosity sclerosis and/or cysts
  • posterior humeral head osteochondral lesions
  • remodeling of the posterior glenoid rim
  • Bennett lesion

Key features are 4-6:

  • articular-sided tears of the posterior supraspinatus and anterior infraspinatus tendons
  • posterosuperior labral tear or fraying or type IIB SLAP tear
  • humeral head cysts underlying the infraspinatus tendon

Additional features include 4:

  • anterior capsule laxity
  • posterior capsule thickening

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Cases and figures

  •  Case 1
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  • Case 2: PASTA Lesion
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