The infraspinatus tendon inserts on the middle facet of the greater tubercle just posterior to the supraspinatus, and isolated infraspinatus tears are less common than supraspinatus tears because the infraspinatus receives better blood supply and is protected from direct subacromial impingement. Infraspinatus tendon tears are clinically identified by weakness of resisted external rotation with the arm at the side (Patte test) and reduction in external rotation strength. They frequently accompany supraspinatus tears in posterior superior cuff tear patterns.
External rotation force transmission; posterior glenohumeral compression and stabilisation
Isolated infraspinatus atrophy on MRI — appearing as fatty infiltration of the infraspinous fossa without supraspinous involvement — is pathognomonic of suprascapular nerve compression at the spinoglenoid notch by a ganglion cyst arising from a posterior labral tear. This pattern must be recognised as suprascapular nerve pathology rather than a rotator cuff tear. Posterior superior cuff tears involving both supraspinatus and infraspinatus require larger repair constructs and have higher re-tear rates than isolated supraspinatus repairs.
External rotator cuff tear usually associated with supraspinatus tears producing external rotation weakness confirmed by the Patte test and managed with arthroscopic repair.
Spinoglenoid notch ganglion compression of the suprascapular nerve producing isolated infraspinatus atrophy without supraspinatus involvement, managed with ganglion aspiration or arthroscopic cyst decompression with labral repair.
