Which criterion is NOT part of the Ottawa Knee Rule for obtaining knee radiographs after an acute injury?

Which criterion is NOT part of the Ottawa Knee Rule for obtaining knee radiographs after an acute injury?

• A. Age 55 or older.
• B. Isolated tenderness at the patella.
• C. Inability to bear weight for four steps.
• D. Painful knee flexion to 180 degrees.

Answer: (D)

The Ottawa Knee Rule uses a simple set of bedside criteria to decide when a knee X-ray is likely needed after an acute injury. It focuses on identifying fractures with easy-to-check signs: being aged 55 or older increases fracture risk, tenderness at specific locations (such as the patella or the head of the fibula) points to possible fracture, and functional limitations—specifically, inability to bear weight for four steps and inability to flex the knee to 90 degrees—also raise concern for fracture. If none of these criteria are present, radiographs are often unnecessary in adults.

The option describing pain with knee flexion to 180 degrees isn’t part of the rule. The threshold is the inability to bend the knee to 90 degrees, not pain with full range of motion. So this choice does not trigger a radiograph under the Ottawa Knee Rule. The other listed criteria are indeed part of the rule, which is why they would influence the decision to image.