MR imaging of the meniscus

MRI plays a central role in the work-up of a patient with suspected knee pathology because of its exquisite contrast resolution and ability simultaneously to display the osseous and soft tissue structures of the knee in virtually any plane. Although meniscal injuries are extremely common, the clinical history is usually nonspecific. Locking, grinding, or joint line tenderness and positive Lachman's or McMurray's tests are suggestive, but not conclusive, of meniscal pathology, and other types of intra- and extra-articular pathology may confound the clinical picture [1]. MRI is the modality of choice for evaluating a patient with suspected meniscal pathology. Its accuracy for detecting meniscal tears is greater than 90% in most series [2-5]. By displaying the morphology of the tear it provides valuable information for determining the need for operative intervention and predicting the feasibility of meniscal repair. If the scan demonstrates only an extra-articular cause for the patient's symptoms (eg, an osseous contusion), it may obviate an unnecessary arthroscopic procedure. This article discusses meniscal anatomy and pathology, the MRI appearance of each, and common pitfalls encountered when evaluating MRIs of these structures. Throughout, an attempt is made to discuss these features in the context of what is most important to the surgeon who is evaluating a patient presenting with a potential meniscal tear.