Our first hypothesis was also proven wrong; when we found that there was no statistically significant difference in the metabolic activity in muscle bellies of normal shoulders and those with rotator cuff tears. Our second hypothesis was proven wrong when found that there was no statistically significant difference in the metabolic activities of rotator cuff muscles between high-grade and low-grade fatty atrophy groups. The metabolic activities of the middle deltoid and trapezius are inversely related. Based on the findings of our study, fatty atrophy or fatty infiltration alone cannot be considered a limiting factor for rotator cuff repair.