ROTATOR INTERVAL
The long head of biceps undertakes a near 90 degree turn as it exits the shoulder joint.
The constraining mechanism which facilitates this is the rotator sling or pulley.
The rotator interval or anterior interval is the area between the subscapularis and supraspinatus tendon

The structures of the rotator pulley are primarily the coracohumeral and superior glenohumeral ligaments.
The coracohumeral ligament receives contributions from the superior glenohumeral ligament more proximally and fibres from the subscapularis tendon more distally.
The most superficial fibres are components of subscapularis and supraspinatus which cross each other

The two pathologies that affect the rotator interval are coracohumeral ligament tears and adhesive capsulitis (frozen shoulder).
Tears of the coracohumeral ligament most often occur in conjunction with other injuries to the rotator cuff.
When the coracohumeral ligament is torn, the biceps tendon is free to sublux or dislocate.
In frozen shoulder, Look for thickening and abnormal internal structure (decreased reflectivity)
Increased vascularity may indicate adhesive capsulitis
IMAGING
Both MRI and ultrasound demonstrate the rotator interval well
US probably shows the internal structure better
The coracohumeral ligament attaches on the lateral margin.
The medial margin is reenforced by the superior glenohumeral ligament

Tears result in:

      • Defects in the ligaments themselves
      • Increased distance between the biceps and leading edge of supraspinatus
      • Reduction in the distance between biceps tendon and subscapularis
      • Frank dislocation of biceps