The Ottawa Knee Rule calculator is a practical tool for determining whether knee imaging is warranted based on a set of specific patient criteria. This evaluation is essential for efficiently guiding clinical decisions regarding the necessity of radiographic examinations for knee injuries.

To use this tool, consider the following five criteria, each a yes/no question about the patient's condition:

- Is the patient aged 55 years or older?
- Is there tenderness at the fibular head?
- Is there isolated tenderness of the patella?
- Is the patient unable to flex the knee to 90 degrees?
- Is the patient unable to bear weight both immediately after the injury and later in the emergency department?

Each “yes” response contributes a score of 1, while a “no” response contributes 0. The scores for each criterion are then summed, resulting in a total score ranging from 0 to 5.

The interpretation of the score assists clinicians in deciding whether imaging is needed:
- A score of 0 suggests that knee imaging is not necessary, indicating a lower likelihood of significant injury.
- A score of 1 or more means that a knee imaging study should be considered, as the probability of a clinically important injury is higher.

The Ottawa Knee Rule is a clinical tool designed for the assessment of patients with acute knee injuries. It aids in determining the need for radiographic imaging, thereby reducing unnecessary exposure to radiation and healthcare costs. The target patient population includes those presenting with acute knee trauma.

The primary components of the Ottawa Knee Rule include age (55 years or older), tenderness at the fibular head, isolated tenderness of the patella, inability to flex the knee to 90 degrees, and inability to bear weight both immediately and in the emergency department. Each of these components contributes to the overall assessment of the patient's injury severity and the subsequent need for radiographic evaluation.