The evaluation of the quality of rotator cuff muscles has become an important part of the preoperative ultrasound examination. Ultrasound is accurate in the evaluation of rotator cuff integrity, but has been found to be insufficient compared to magnetic resonant imaging (MRI) in the evaluation of rotator cuff muscle quality. Complete tears of the rotator cuff lead to muscle atrophy and fatty infiltration, these changes are known to be important negative prognostic factors with regard to the anatomical and functional results after tendon repair. Several classifications and grading systems have been described for computed tomography (CT) and MRI. A number of studies have been directed at the ultrasound assessment of muscle atrophy and fatty infiltration of the rotator cuff, however, no quantitative method or grading systems have been established. At present MRI is the preferred choice for evaluation of rotator cuff fatty infiltration and muscle atrophy in clinical practice. Ultrasound is widely available, cost effective and safe; the aim of this literature review is to investigate if there is a role for ultrasound in the examination of rotator cuff muscle quality.