 Basic Science small animal model data indicates that matrix metalloproteinase MMP inhibition via doxycycline results in improved early rotator cuff repair biomechanics and histology. Rotator cuff repair failure and retear is a significant clinical problem. The effects of MMP inhibition on human rotator cuff tear repair healing and outcomes is unknown, but may potentially improve healing rates and outcomes. Our purpose is to evaluate the effects of early oral doxycycline on healing and outcomes following arthroscopic rotator cuff repair. 