Postoperative Imaging of the Knee

This issue of Seminars in Musculoskeletal Radiology focuses on the spectrum of imaging in the postoperative knee. Musculoskeletal imaging has continued to evolve over the years, and the advancement in imaging techniques and interventions continues to maintain our subspecialty's prominence in patient care. Postoperative imaging interpretation is often complex and challenging; as such, an organized, systematic approach is essential in distinguishing between expected postoperative changes and new or existing pathology. Review of the patient's clinical and surgical history and pretreatment imaging studies aids in diagnosis. This issue includes 10 selected manuscripts that provide practicing radiologists, residents, and fellows the most accurate and current update on postoperative knee imaging.

The first article comes from Felix Wuennemann, MD, and colleagues at the University Hospital of the University of Heidelberg and University Medical Center Rostock on “Imaging of the Knee Following Repair of Focal Articular Cartilage Lesions.” This article reviews the pre- and postoperative imaging of focal articular cartilage lesions, the classification of these lesions, and cartilage repair techniques. The next article, “Knee Imaging Following Anterior Cruciate Ligament Reconstruction: The Surgeon's and Radiologist's Perspective” by Ramya Srinivasan, MD, and colleagues from University of California San Francisco, nicely reviews the surgical techniques for anterior cruciate ligament (ACL) reconstruction and highlights recent technical advances from a surgeon's perspective. The normal imaging appearance after ACL reconstruction is reviewed along with etiologies for reconstruction failure, complications that may occur, and magnetic resonance imaging (MRI) features that accompany these cases.

Meniscus surgery is very common, and imaging the postoperative meniscus requires understanding of the basic anatomy and biomechanics of the knee together with possible surgical interventions. Andrew Cordle, MD, PhD, and colleagues from the University of Pittsburgh Medical Center discuss “The Postoperative Meniscus: Anatomical, Operative, and Imaging Considerations.” The authors review the anatomy, operative techniques, and imaging interpretation in this common postsurgical evaluation.

The complex anatomy and biomechanics of the posterolateral corner (PLC) of the knee has received much attention in the literature within the last 2 decades. Ali Naraghi, FRCR, and colleagues from Toronto Western Hospital and St. Michael's Hospital take this a step further with “Imaging of the Postoperative Condition of Posterolateral Corner Injuries.” This article reviews the more commonly used surgical techniques and the postoperative imaging assessment of the PLC to aid in our understanding of this complex area. The following article by Jeremiah Long, MD, and David Rubin, MD, at Mallinckrodt Institute of Radiology, St. Louis, reviews the “Postoperative Imaging of the Knee Extensor Mechanism.” The pathophysiology, surgical indications, and operative techniques used for extensor mechanism injuries are discussed as well as a review of the normal and abnormal postoperative imaging findings to guide in accurate interpretation.

Shifting gears, the next article by Ioan Gemescu, MD, and colleagues from University Emergency Hospital Bucharest, the university hospitals of Heidelberg and Rostock, as well as the Hospital for Special Surgery in New York covers “Assessment of Loosening and Rotational Malalignment Following Knee Endoprosthesis or Other Surgical Components.” The authors review the most relevant information in the evaluation of knee endoprosthesis alignment and review how to perform appropriate measurements. This is followed by “Dedicated CT and MRI Techniques for the Evaluation of the Postoperative Knee” by Iman Khodarahmi, MD, and colleagues from Johns Hopkins University School of Medicine, Baltimore. They review the latest advancements in computed tomography and MRI metal artifact reduction techniques to enhance assessment of prosthetic joints.

An article by Hatice Tuba Sanal, MD, at the Health Sciences University, Gülhane Medical School, Ankara, and coauthors at the Medical University of Vienna reviews the “Imaging Following Fracture of and Around the Knee.” It includes a discussion of operative techniques and the complications that can be encountered. Postoperative infections of the knee are uncommon; however, failure to recognize them in a timely fashion may lead to devastating consequences. The next article by Mihra Taljanovic, MD, PhD, FACR, from the University of Arizona and colleagues from Northwestern University Feinberg School of Medicine, Medical University Innsbruck, and University Orthopaedic Specialists, Tucson, exquisitely describes the “Imaging of Postoperative Infection at the Knee Joint” including multiple imaging methods and their appearances in the setting of infection. The final article is on “Imaging of the Knee and Surrounding Structures Following Tumor Surgery” by Naomi Winn, MBBC, BMedSci, and Radhesh Lalam, FRCR, from The Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry. They review the normal expected imaging appearances and complications following tumor surgery.

We expect this issue will provide a helpful update on many challenges that are encountered in the evaluation of the postoperative knee. We would like to thank each of the authors for contributing their time and expertise to this outstanding issue. We hope you find a useful pearl or two to take away from this edition that will aid in your musculoskeletal interpretation.