The painful knee: choosing the right imaging test.

The initial evaluation of acute knee pain should include plain radiography, which is a quick and cost-effective way to identify a wide range of problems, including fracture, degenerative changes, osteochondral defects, and effusions. Computed tomography (CT) is the test of choice to better delineate fractures in patients who have knee trauma. If the history and physical examination point to damage of the cartilage, the menisci, and the cruciate and collateral ligaments and arthroscopy is contemplated, then magnetic resonance imaging (MRI) is useful for evaluating these structures.