Smith GCS, et al. - A systematic review was performed to determine whether a high critical shoulder angle (CSA) is associated with symptomatic full-thickness rotator cuff (RC) tears and/or whether a low CSA is associated with primary glenohumeral osteoarthritis (GHOA). Researchers enrolled all observational studies that examined a correlation between CSA and full-thickness RC tears and/or primary GHOA. Eleven studies met the inclusion criteria for RC tears and 5 for primary GHOA for the primary meta-analysis. A secondary meta-analysis was conducted to investigate the hypothesis that radiographic quality was a source of heterogeneity, which eliminated those studies in which radiograph quality was not strictly determined and controlled. When assessing symptomatic full-thickness RC tears vs primary GHOA as compared with control subjects, there is a reciprocal change in the magnitude of the CSA. It was noted that radiographic quality is a source of heterogeneity in studies that examine a link between CSA and RC tears and primary GHOA.