Although surgical techniques have advanced to avoid a postoperative re-tear after rotator cuff surgery, it remains unclear how to directly evaluate the risk of a re-tear./r/nTo describe how muscle elasticity with real-time tissue elastography could be used to avoid re-tear in individual cases after rotator cuff repair./r/nThis case series included four patients, two per tear size (small and large/massive), with contrasting changes in muscle elasticity of the supraspinatus muscle. All patients underwent primary arthroscopic or open rotator cuff repair. The elasticity of the supraspinatus muscle was evaluated at relaxed and elongated positions of 0° and 60° shoulder abduction angles, respectively. The change in muscle elasticity at 1 month after surgery was characteristically different, and we predicted that a greater elasticity in the elongated position indicated a higher risk of re-tear. The cases with high risk underwent careful rehabilitation to avoid re-tear, and no re-tears were recorded in this report./r/nOur findings suggested that evaluation of muscle elasticity using real-time tissue elastography, which provides an indication of the risk of re-tear, in the clinical setting might be useful for therapists, who could adjust the intensity of rehabilitation, and for patients.