Normal and variant anatomy of the shoulder on MRI.

New developments in musculoskeletal magnetic resonance (MR) imaging, including improved spatial resolution and MR arthrography, have led to an increasing frequency in the performance of shoulder MR imaging. As a result, radiologists' understanding of the normal and variant anatomy of the shoulder visible on MR imaging has also become more important. In this article, the authors review the normal arrangement and appearance of osseous and soft-tissue structures in the shoulder, as well as nonpathologic osseous and nonosseous variants that should be recognized.