X-ray is only required in patients who have an acute injury and one or more of the following:
Age >55
Isolated tenderness of the patella
Tenderness at the fibular head
Inability flex to 90 degrees
Inability to walk 4 steps BOTH immediately after the injury and in the ED
Ottawa knee rules
Ottawa ankle rules
SAD PERSONS score
Arthrocentesis: ankle
Arthrocentesis: elbow
Arthrocentesis: knee
Arthrocentesis: hip
Arthrocentesis: shoulder