MR and internal derangement.

65 RADIOLOGIC TECHNOLOGY September/October 2006, Vol. 78/No. 1 Knee pain is a common reason for patient visits to a physician office. Cluette suggests common causes of knee pain, including arthritis, ligament injuries, cartilage injuries, meniscal tears, patellar tendonitis, chondromalacia patella, Bakers cyst, bursitis, Osgood-Schlatter disease, osteochondritis dissecans and gout. Certainly there are other causes; the job of imaging professionals is to facilitate the diagnosis of such ailments. In the past, plain film radiography was used as the first imaging modality to aid the evaluation of the painful knee; however, today plain films are used primarily to evaluate joint space narrowing and for major trauma events. Positions for these cases include the traditional posteroanterior (PA) projections and lateral positions. Additionally, joint space narrowing is demonstrated by weight-bearing knee studies such as the Rosenberg method. Because of the many soft tissue structures within the knee, it is impossible to adequately evaluate the knee joint with plain radiographs. In fact, “[O]ver the past 15 years, magnetic resonance (MR) imaging has become the premier, first-line imaging study that should be performed in the evaluation of the painful knee.” This article describes some of the soft tissue components of the knee joint. Injury occurs when these structures become damaged, usually with resultant tendon, cartilage or ligament tears. Traumatic injury can be a major cause of knee problems, but damage can also be attributed to physiological processes such as gene mutations. Furthermore, this article defines internal derangement and concludes with an example of a torn meniscus demonstrated by the use of MR imaging.