IntroductionDifferences between radiologists and orthopaedic surgeons in the interpretation of MR images of the shoulder joint are experienced in daily clinical practice. This study set out to evaluate the inter-observer agreement between radiologists and orthopaedic surgeons in assessing pathology on MR imaging of the shoulder joint. Also, we determined the accuracy of the observers with arthroscopy as the standard of reference.Materials and methodsTwo radiologists and one orthopaedic surgeon reviewed 50 MR studies—25 conventional MR examinations and 25 MR arthrographies—of patients with shoulder complaints who had undergone MR imaging and subsequently arthroscopic surgery. The assessment was independent and blinded. All observers evaluated the MR examinations twice. Standard evaluation forms were used to score for pathology of rotator cuff, glenoid labrum, tendon of the long head of the biceps brachii and glenohumeral ligaments. The presence or absence of osteoarthritis, SLAP lesions, Bankart lesions, Hill-Sachs lesions or impingement was also noted. Intra- and inter-observer agreement, the sensitivity and specificity were calculated. Differences in percentages of correctly diagnosed lesions were tested for significance using McNemar’s test.ResultsThere was a poor inter-observer agreement between the orthopaedic surgeon and the radiologists in assessing Bankart lesions and ligamentous lesions. We found significant differences between the radiologists and the orthopaedic surgeon in the assessment of osteoarthritis, Hill-Sachs lesions and impingement.ConclusionThe orthopaedic surgeon and radiologists differed in their interpretation of what defines a Bankart lesion and what defines a ligamentous lesion. The orthopaedic surgeon was significantly more accurate in assessing impingement.