Stress radiographs in the diagnosis of patellofemoral instability

Abstract

Importance: Stress radiographs provide the only available objective measurement of PF joint instability. The diagnosis of joint instability is only confirmed by demonstrating the pathological separation of joint surfaces. This is normally accomplished by applying stress to the joint and demonstrating an abnormal displacement of the two surfaces. Measuring this displacement is needed to document the test result. Nonspecific criteria such as pain or apprehension are frequently used as circumstantial evidence for making the diagnosis of joint instability. Pain and apprehension may be the result of conditions not related to joint instability such as arthrosis. A demonstration of excess displacement is evidence of instability but the amount of displacement should be documented by a valid measurement tool. © 2010 Springer-Verlag Berlin Heidelberg.