A knee radiograph is required only for acute knee injury patients with one or more of the following findings:
• Age 55 years or older
• Tenderness at the head of the fibula
• Isolated tenderness of the patella
• Inability to flex to 90 degrees
• Inability to bear weight for four steps both immediately and in the ED
• The derived clinical decision rule was 100% sensitive and 54% specific.
• The derived clinical decision rule predicts a 28% reduction in radiography.