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BackgroundPrevious studies on shoulder patients have suggested that the prevalence of rotator cuff or bursa abnormalities are weakly related to symptoms and that similar findings are often found in asymptomatic persons. In addition, it is largely unknown whether structural changes identified by magnetic resonance imaging (MRI) affect outcome after treatment for shoulder pain. The purpose of this study was therefore to evaluate the presence of structural changes on MRI in patients with subacromial pain syndrome and to determine to what extent these changes are associated with symptoms and predict outcome after treatment (evaluated by the Shoulder Pain and Disability Index (SPADI)).MethodsA prospective, observational assessment of a subset of shoulder patients who were included in a randomized study was performed. All participants had an MRI of the shoulder. An MRI total score for findings at the AC joint, subacromial bursa and rotator cuff was calculated. Multiple linear regression analysis was applied to examine the relationship between the MRI total score and the outcome measure at baseline and to examine to what extent the MRI total score was associated with the change in the SPADI score from baseline to the one year follow-up.ResultsThere was a weak, inverse association between the SPADI score at baseline and the MRI total score (β = −3.1, with 95% CI −5.9 to −0.34; p = 0.03), i.e. the SPADI score was higher for patients with a lower MRI total score. There was an association between the change in the SPADI score from baseline to the one year follow-up and the MRI total score (β = 8.1, 95% CI -12.3 to −3.8; p < 0.001), with a poorer outcome for patients with a higher MRI total score. Both tendinosis (p = 0.01) and bursitis (p = 0.04) were associated with a poorer outcome after one year.ConclusionsIn this study, MRI findings were significantly associated with the change in the SPADI score from baseline and to one year follow-up, with a poorer outcome after treatment for the patients with higher MRI total score, tendinosis and bursitis on MRI.Trial registrationClinicaltrials.gov no NCT01441830. September 28, 2011.