A positive pre-operative ultrasound scan at our institution predicts an actual rotator cuff tear in 70% of cases. However, it is not accurate with respect to identifying partial-thickness tears or distinguishing them from full-thickness defects. Ultrasound scanning is highly operator dependent and, in addition, its accuracy may be affected by the lengthy time period from scanning to surgery. Clinicians should be cautious in proceeding to surgery based on the ultrasound findings.