Posterosuperior impingement comprises the triad of:
posterosuperior labral tear
joint surface partial tear of the junctional area between supraspinatus and infraspinatus
bony signal changes in the posterosuperior quadrant of the humeral head
Clinically there is progressive reduction in the range of shoulder internal rotation (GIRD)
Possibly due to capsular thickening in the region of the posterior limb of the iGHL.
Proposed that this abnormal motion leads to impingement of the posterosuperior labrum forcing it over the superior glenoid margin.
This has been called the peelback phenomenon. The joint surface partial tear in this scenario is attributed to a chronic torsional injury.
The tear of the posterior labrum may be complicated by a paralabral cyst, which in turn can compress the suprascapular nerve and lead to infraspinatus atrophy
