MR of the Knee: Important But Less-Often Discussed Structures and Pathology

The knee is the most common joint examined with magnetic resonance (MR) imaging, and an extensive and impressive collection of articles describe both normal anatomy and abnormal pathology of the knee. Most of these articles concern the most frequently injured structures in the knee, the menisci and cruciate ligaments, and the literature has documented the excellent accuracy of MR in diagnosing abnormalities of these structures. However, as all of us who read MR of the knee everyday know, we often have more difficulty and spend much time diagnosing the anatomy of and abnormalities of structures less commonly discussed: the collateral ligaments, articular cartilage, bone marrow, synovium, and extensor mechanism. It is these structures that this issue of Seminars in Musculoskeletal Radiology concentrates on in an effort to clarify their normal anatomy and MR appearance as well as common abnormalities and variants seen on MR imaging.

We are fortunate to have enlisted an impressive collection of contributors for this issue. Drs. Chung, Boucher, and Resnick provide an excellent and comprehensive discussion of synovium and synovial pathology. Dr. Goodwin, one of the leaders in the field, brings us up to date on the state of the art of MR imaging of articular cartilage. Dr. Miller has tackled the difficult subjects of the medial and lateral stabilizers of the knee with a thorough discussion of their complex anatomy and associated pathology. Dr. Subhas and colleagues have contributed an excellent discussion of incidental findings in the bone marrow and soft tissue, a problem I am sure all of us face daily, and they explain when to ignore and when to follow up these findings. Bone marrow signal changes are a frequent finding on MR imaging of the knee, and Drs. Rajmane and Schweitzer have written a thorough description of posttraumatic bone marrow changes. Drs. Kramer, White, and I have tackled the extensor mechanism, whose anatomy and pathology can be troublesome.

We would like to thank all of the contributors and hope this issue helps evaluate these less commonly discussed structures of the knee.