BACKGROUND: With a substantial portion of the population experiencing rotator cuff pathology, the importance of understanding mechanisms of rotator cuff disease remains critical. Current research aimed at understanding relationships between shoulder movement and cuff injuries has been hindered by our limited knowledge of the thickness of soft tissue structures within the shoulder. Therefore, the purpose of this study is to measure the thicknesses of all four rotator cuff tendons at the articular margin. METHODS: An anatomic study of 21 cadaveric shoulders was conducted. The thicknesses of the four rotator cuff tendon insertions were measured by caliper at the articular margin. RESULTS: The mean thickness of the supraspinatus at the articular margin was 4.9 mm ± 2.1 (median: 4.2 mm, range: 2.9-12.7 mm). The mean thickness of the infraspinatus tendon was 4.9 mm ± 1.3 (median: 4.8 mm, range: 3.0-7.2 mm). The mean thickness of the teres minor tendon was 3.20 mm ± 1.14 (median: 2.9 mm, range: 1.7-5.7 mm). Finally, the mean thickness of the subscapularis tendon at the articular margin was 5.5 mm ± 1.3 (median: 5.5 mm, range: 3.5-9.3 mm). CONCLUSIONS: This current study provides needed objective data about the thickness of the rotator cuff tendons at the articular margin. Data regarding the infraspinatus, teres minor and teres major, which have been largely understudied, are particularly important. In addition, the current study demonstrates that rotator cuff thicknesses can vary substantially between individuals. There are likely natural age related changes as well as changes from etiologies that are not yet elucidated. Clinical Relevance: Data from this study will allow for improved modelling accuracy of soft tissue structures specific to the shoulder. Eventually knowledge gained through study of shoulder mechanics can be used to pursue prevention of rotator cuff tears and improve targeted treatment planning.