The Knee: Update on Imaging and Intervention

This issue of Seminars in Musculoskeletal Radiology focuses on relatively recent developments in the knowledge and understanding of knee imaging, mechanisms of injury, and both surgical and percutaneous treatment of soft tissue and osseous disorders of the knee. Increased sophistication of ultrasound (US) and magnetic resonance imaging (MRI) has allowed radiologists to appreciate and diagnose the complex soft tissue anatomy of the knee in much greater detail than previously possible, thus affording greater contribution in directing new surgical and imaging-guided percutaneous treatments.

The first article by Drs. Ariyachaipanich, Bae, Statum and Chung, from the University of California, San Diego, describes recent developments in MRI pulse sequences of the knee, focusing on new applications of current pulse sequences to the diagnosis of abnormalities of cartilage, meniscus, tendon, and hardware. Increased MR resolution has enabled radiologists to appreciate that anterior and posterior cruciate ligaments rarely rupture in isolation but are accompanied by extensive additional ligamentous and soft tissue injuries. MRI diagnosis of multiligamentous injury using a mechanism or pattern-based approach is discussed by Drs. Hansford and Yablon (from Utah and Michigan Universities, respectively). Drs. A. and M. Geeslin and LaPrade, from the Steadman Philippon Research Institute in Vail, Colorado, have written a complementary article on what orthopaedic surgeons would like radiologists to know about ligamentous reconstruction of the knee, providing a valuable surgical perspective. Dr. LaPrade's research has made enormous contributions to the advancement of radiologists' and orthopaedic surgeons' understanding of ligamentous anatomy and injury about the knee.

Drs. McMahon and Ramappa of the Beth Israel Medical Center in Boston, and Dr. Lee from the University of Wisconsin discuss the diagnosis and treatment of extensor mechanism injury including patellar tracking disorders, patellar and quadriceps tendon injury, and patellar fracture. Dr. Jacobson from the University of Michigan and colleagues have written a complementary article sharing their expertise in the comprehensive sonographic evaluation of the knee, advancing our understanding and application of US to diagnose and treat other soft tissue abnormalities including arthritis, parameniscal cyst, joint effusion, Baker's cyst, ligament and other tendon injury, and peripheral nerve and vascular abnormalities.

Drs. Rowbotham and Grainger, from Leeds Teaching Hospitals, United Kingdom, discuss the use of MRI not only in diagnosing osteoarthritis of the knee and subtle additional findings, but in monitoring the response to treatment. MR imaging features of inflammatory and crystalline arthritides are also reviewed. Drs. Morag and Yang, from the University of Michigan, describe how MR neurography and high-resolution US enhance our ability to diagnose peripheral nerve disorders about the knee, and are complementary to physical examination and electrophysiologic studies. Drs. Leschied and Udager of the University of Michigan discuss MRI of pediatric knee injuries, a topic of particular interest given the marked increases in participation and level of competition seen in youth sport over the past few decades.

Lastly, Drs. Bai and Ha from the University of Washington and Dr. Thomas of Penn State Hershey Medical Center present a comprehensive discussion of the wide range of surgical treatment options available for osteochondral injury and osteoarthritis, including palliative, restorative and reparative procedures, and joint reconstruction. They review both pre- and postoperative imaging and complications of these procedures.

As guest editor of this issue, I thank all of the authors for sharing their knowledge and expertise with our readers, and I also very much appreciate the time they spent preparing these excellent articles. In addition, I would like to thank Dr. Laura Bancroft for the invitation to edit this issue and for providing guidance from concept to publication.