Myosteatosis, also known as fatty infiltration, is the pathological accumulation of lipid that occurs in conjunction with atrophy and fibrosis following rotator cuff injury. Little is known about the mechanisms by which lipid accumulates in myosteatosis, but many studies have demonstrated the degree of lipid infiltration negatively correlates with muscle function and regeneration. Identifying how reduced mechanical loading activates molecular pathways that lead to myosteatosis could help to develop targeted therapies to improve functional outcomes after rotator cuff repair. Our objective was to use cutting compare muscle fiber contracility, proteomic, RNA sequencing and shotgun metabolomics along with bioinformatics to identify potential pathways and cellular processes that are dysregulated after rotator cuff teaar.