Abstract
OBJECTIVE: Radiographic osteoarthritis of the acromioclavicular joint (ACJ OA) is a common incidental finding and an uncommon reason for people to seek care for shoulder symptoms. We reviewed the published evidence regarding the age-specific prevalence of ACJ OA to establish the base rate of pathophysiology. METHODS: A total of 10 studies including 1831 shoulders met our criteria. A pooled analysis was done to obtain a proportion of subjects with ACJ OA across age categories. RESULTS: Forty-eight percent of 953 cadaver and skeletal specimens and 70% of 210 MRI images of asymptomatic shoulders were found to have changes consistent with ACJ OA. Four studies reporting age as a continuous variable found a statistically significant association between older age and prevalence of ACJ OA. CONCLUSIONS: The observation that ACJ OA is highly prevalent as humans age establishes a very high base rate of what one can infer is well-accommodated disease. Given that a high base rate of incidental disease creates a low pre-test odds that radiological findings of disease correspond with symptoms, diagnosis of symptomatic ACJ OA is subject to substantial inaccuracy and should be made sparingly, mindful of the potential harms of a diagnosis that can lead to an ablative surgery.