Previously, we reported that the footprint of the supraspinatus on the greater tuberosity is much smaller than previously believed, and the footprint is actually occupied by a substantial amount of the infraspinatus. The purposes of this study were to analyze our operative outcomes of arthroscopic repair for small and medium rotator cuff tears and to determine retrospectively the locations of tear sites based on our new anatomical concepts. A total of 30 shoulders of patients (13 females, 17 males) underwent arthroscopic cuff repair for small and medium tears from 2007 to 2008. The mean age at surgery and the mean follow-up period were 65 years old (average, 51 to 81) and 10 months (average, 6 to 24),respectively. The distributions of the torn site were analyzed with preoperative magnetic resonance imaging (MRI) using bony landmarks. The clinical outcomes were evaluated using the JOA shoulder score. Based on preoperative MRIs, torn sites of 6 cases were located at the anterior side of the highest impression of greater tuberosity. Torn sites of 21 cases were located from the anterior side of the highest impression to the middle impression, and that of 3 cases were difficult to determine. The average total JOA score improved from 60.7 to 92.4. Based on our new anatomical concepts, the present study showed that infraspinatus tears were included in small and medium tears more than previously described.