OBJECTIVE: To evaluate the diagnostic performance of magnetic resonance (MR) arthrography of the shoulder in the diagnosis of anteroinferior labrum lesions, using arthroscopy as the reference standard and to classify these lesions.METHODS: Institutional review board approval was obtained. The study population included 59 consecutive patients with history and clinical diagnosis of acute or chronic anterior shoulder instability. A total of 62 MR arthrograms were performed, since three patients had undergone a bilateral procedure. Arthroscopy, which was performed within a mean of 3 months (range 2-5 months) after MR arthrography, was used as the reference standard. Sensitivity, specificity, accuracy, positive and negative predictive values were then calculated.RESULTS: MR arthrography showed a sensitivity of 96 % and a specificity of 80 % for the overall detection of anteroinferior labrum abnormalities. The diagnostic accuracy was 95 % and the positive and negative predictive values were 98 % and 66 % respectively. Ten lesions were non-classifiable on surgery, of which eight were non classifiable on MR arthrography also.CONCLUSIONS: MR arthrography is highly accurate for the detection and classification of shoulder anteroinferior labrum lesions. Shoulder surgeons can confidently rely on this method to determine which patients will benefit from arthroscopy.MAIN MESSAGES: • MR arthrography is accurate for the detection and classification of shoulder labrum lesions. • MR arthrography is a valuable tool for the preoperative planning in acute or chronic instability. • Shoulder surgeons can rely on this method to determine which patients will benefit from arthroscopy.