Ultrasonography, provided by a single experienced orthopaedic surgeon (K.F.) using a portable ultrasound machine (SSA-640 Viamo; Toshiba Medical Systems) with linear-array probes at 12 MHz, was used to examine both shoulders to diagnose rotator cuff tears. During ultrasonographic examination, the shoulder position was kept in slight extension and neutral rotation. The torn rotator cuff tendon was identified by using the short axis of the ultrasonographic image, according to a previous anatomic study. When the defect was at the superior facet of the greater tuberosity, we diagnosed a supraspinatus tendon tear. A defect in the middle facet of the greater tuberosity was diagnosed as an infraspinatus tendon tear. Partialthickness tears of the rotator cuff demonstrated an increase in the echogenic signal intensity and/or a focal decrease in the thickness of the tendon. For partialthickness rotator cuff tears, tear depth was measured by using the long axis of the ultrasonographic image (Figure 1).