The Acute Patella Injury Test (aka Apprehension Test) is used to assess the possibility that the patient may have sustained a patellar dislocation which spontaneously reduced. This test provokes the same sensations which would have been present when the dislocation occured and therefore will elicit a reactive contraction of the quadriceps muscles by the patient in an attempt to avoid a recurrance of the dislocation. This reaction is referred to as an apprehension sign. The patient lies supine on the table with the knee in 20-30 degrees of flexion and the quadriceps relaxed. The examiner carefully glides the patella laterally observing for the apprehension sign. A positive test is the presence of this reaction by the patient.