ACR appropriateness criteria(®) acute trauma to the knee.

There are more than 1 million visits to the ER annually in the United States for acute knee trauma. Many of these are twisting injuries in young patients who can walk and bear weight, and emergent radiography is not required. Several clinical decision rules have been devised that can considerably reduce the number of radiographic studies ordered without missing a clinically significant fracture. Although fractures are seen on only 5% of emergency department knee radiographs, 86% of knee fractures result from blunt trauma. In patients with falls or twisting injuries who have focal tenderness, effusion, or inability to bear weight, radiography should be the first imaging study performed. If radiography shows no fracture, MRI is best for evaluating for a suspected meniscal or ligament tear or patellar dislocation. Patients with knee dislocation should undergo radiography and MRI, as well as fluoroscopic angiography, CT angiography, or MR angiography. The ACR Appropriateness Criteria(®) are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.