Project Summary—Abstract Healing following rotator cuff repair (RCR) remains a significant clinical challenge. While most patients report improvements in clinical outcomes, approximately 20-30% experience a retear by 6 months. Failure of RCR healing can lead to significant clinical consequences, initiating a pathologic progression associated with worsening pain, function, and strength, and an increased risk of re-operation over time in some patients. However critical knowledge gaps persist in our understanding of the significance of RCR healing, the roles of other patient and surgical factors, and development of degenerative changes in determining longer-term clinical outcomes. Our proposal addresses these gaps by leveraging two ongoing prospective RCR cohorts of 161 patients being followed at our institution to collect comprehensive, and in some instances, first-of-kind data on shoulder pain and function, RCR healing, and associated degenerative shoulder pathology over 5 years following RCR. Aim 1 will measure and describe the evolution of clinical outcomes and degenerative changes over 5y following RCR using traditional and novel potentially more sensitive variables. Aim 2 will estimate the prognostic effect of 1y RCR healing status on clinical outcomes and on the evolution of degenerative shoulder pathology over 5y following RCR. Aim 3 will develop and provide online calculators for preoperative clinical prediction of 5y ASES score under alternative healing scenarios. The unique collection of longitudinal data on RCR healing and joint pathology in combination with clinical outcomes will offer valuable insights into the progression and severity of declining clinical and pathologic outcomes after RCR. This will enhance our understanding of the benefits of successful RCR healing and guide clinical decisions regarding targeted strategies to improve RCR healing. The online calculators would have immediate clinical impact by helping to identify and appropriately manage patients at risk for poor longer-term outcomes, thus facilitating the use of strategies to improve healing where needed.