Abstract: Background: Aim of this study was to investigate the potential influence of Critical Shoulder Angle (CSA) as a predisposing factor for the development of degenerative full-thickness rotator cuff tears (DRCT) or primary glenohumeral osteoarthritis (PGOA). Materials and Methods: This was an observational and prospective study, with subjects presenting with pain and/or restricted motion of their shoulder/s (symptomatic shoulders) presenting to the orthopedic Department and Radiology, Subbaiah Institute of Medical Sciences conducted between December 2019 to August 2020. We divided the subjects into case and control groups on the basis of presence and absence of “non-traumatic RCTs,” respectively, as per their USG (in three patients) and/or MRI shoulder scans. There were 60 study subjects and 60 control subjects. Results: The mean age of the control group was 56.37 years, while that of the study group was 58.42 years. The study group had a predominance of males (58%). About 62% of subjects in the study group had right-sided symptomatic shoulders. The mean CSA of control subjects was 32.63° (±1.87°), while that of study subjects were 36.72° (±2.24°). The minimum and maximum CSA values in the study and control groups as well as their mean, median and mode, with standard deviation. Mean CSA values of study and control groups are represented. Conclusion: The CSA was an objective assessment tool to identify patients with shoulder pain who may have RCTs. Our study indicated that the CSA predicted RCTs more accurately than did the AI for patients with shoulder pain.