From the Guidelines
The Ottawa Knee Rules (OKR) dictate that knee radiographs are necessary for patients 18 years of age or older with acute knee pain if they meet any of the following criteria: are 55 years of age or older, have palpable tenderness over the head of the fibula, have isolated patellar tenderness, cannot flex the knee to 90°, cannot bear weight immediately following the injury, or cannot walk in the emergency room (after taking 4 steps) 1. The OKR are clinical decision guidelines used to determine when X-rays are necessary for patients with acute knee injuries. These rules were developed to reduce unnecessary radiography while maintaining high sensitivity for detecting clinically significant fractures.
- The criteria for knee radiographs include:
- Age 55 years or older
- Palpable tenderness over the head of the fibula
- Isolated patellar tenderness
- Inability to flex the knee to 90 degrees
- Inability to bear weight immediately following the injury
- Inability to walk in the emergency room (after taking 4 steps) By following these criteria, healthcare providers can effectively identify patients who are unlikely to have a fracture (thus avoiding unnecessary X-rays) while ensuring those with a higher probability of fracture receive appropriate imaging, as supported by the study published in the Journal of the American College of Radiology 1. This approach reduces radiation exposure, decreases emergency department wait times, and lowers healthcare costs without compromising patient care, ultimately improving morbidity, mortality, and quality of life outcomes.
From the Research
Ottawa Knee Rules (OKR) Criteria
The Ottawa Knee Rules are a set of criteria used to assess knee injuries and determine the need for radiography. The criteria include:
- Injury due to trauma and age >55 years 2
- Tenderness at the head of the fibula or the patella 2
- Inability to bear weight for 4 steps 2
- Inability to flex the knee to 90 degrees 2
Application of the Ottawa Knee Rules
The Ottawa Knee Rules have been shown to be highly sensitive and specific for identifying patients with fractures of the knee 3, 4. Studies have demonstrated that the rules can be applied by both physicians and triage nurses, although nurses may overestimate the presence of individual components 5, 6. The rules have been validated in various clinical settings, including emergency departments and primary care settings 2, 3, 4.
Benefits of the Ottawa Knee Rules
The use of the Ottawa Knee Rules can help reduce the number of unnecessary radiographs ordered, streamlining patient throughput and allowing for significant cost savings 3. The rules have been shown to be highly reproducible and have a high degree of interobserver agreement 3. Additionally, the rules may be applicable to the pediatric population, although further studies are needed to confirm this 3.
Key Findings
- The Ottawa Knee Rules have a sensitivity of 1.0 (95% CI 0.96 to 1.0) for identifying fractures of the knee 4
- The rules have the potential to reduce the use of radiography by 49% 4
- The probability of fracture, if the decision rules are negative, is estimated to be 0% (95% CI 0% to 0.5%) 4
- Triage nurses and physicians have fair to good agreement in their application of the Ottawa Knee Rules 5, 6