Patellofemoral joint: identification of abnormalities with active-movement, "unloaded" versus "loaded" kinematic MR imaging techniques.

A positioning device was used to apply a "load" to stress the patellofemoral joint during active-movement, kinematic magnetic resonance (MR) imaging. Twenty-three symptomatic patellofemoral joints were studied by using "unloaded" versus "loaded" techniques. With the unloaded technique, seven joints were normal, nine had lateral subluxation, three had lateral tilt, and four had medial subluxation. With the loaded technique, one was normal, 13 had lateral subluxation, four had lateral tilt, and five had medial subluxation. The active-movement, loaded kinematic MR imaging technique provides improved ability to identify patellofemoral joint abnormalities.