Rotator cuff degeneration and cuff tear arthropathy result from chronic degeneration and wear, representing a significant clinical and financial burden in the elderly population. Reverse shoulder arthroplasty (RSA) has proven to be superior in restoring clinical and functional outcomes in patients not amendable to direct rotator cuff repair when compared with total shoulder arthroplasty. However, the design of the reverse shoulder prosthesis fails to restore external rotation in the setting of massive posterior rotator cuff tears with a dislocation rates as high as 9%. This necessitates a review of the role of the remaining posterior rotator cuff (infraspinatus and teres minor) and subscapularis on postoperative clinical and functional outcomes after RSA. On the basis of the available literature, the health of the posterior rotator cuff, reflected in the degree of fatty infiltration and tearing, is essential for maintenance and restoration of external rotation postoperatively, with the integrity of the teres minor being more critical. Proper tensioning of the posterior cuff using increased offset designs is necessary to achieve optimal outcomes. However, tendon transfers using the latissimus dorsi, with or without the teres major, make the contribution of the remaining posterior rotator cuff on postoperative outcomes negligible. Meanwhile, subscapularis repair and integrity are not critical to postoperative stability of the prosthesis or internal rotation. Further investigations are warranted to determine the amount of remaining rotator cuff and the extent of degeneration necessary to impact postoperative outcomes after RSA.