This is an interesting paper for anyone who treats tendon injuries. Most practitioners are aware of the strong connection between fluoroquinolone antibiotics and tendon ruptures, and the connection between type II diabetes and tendon injuries, but more often than not patients presenting for treatment and evaluation of tendon tears do not have their vitamin D levels checked. This is unfortunate because this paper confirms that hypovitaminosis D plays a significant role in the development of rotator cuff tears. The authors of this study performed a retrospective cohort study of 336,000 patients diagnosed with hypovitaminosis D, and showed that these patients were nearly 3 times more likely to experience a rotator cuff tear, and 2.3 times more likely to experience a full-thickness rotator cuff tear within 2 years being diagnosed with hypovitaminosis D. Women with low levels of vitamin D were more likely to undergo surgery for their rotator cuff tears and were significantly more likely to undergo manipulation under anesthesia. The authors state: “While many risk factors for RCT are unmodifiable, vitamin D deficiency is a readily modifiable risk factor with several treatment regimens demonstrating positive effects on musculoskeletal health.”