Ottawa Rules: Clinical Decision Rules for Ankle and Knee Injuries
The Ottawa Rules are validated clinical decision tools that help determine when radiography is necessary for acute ankle and knee injuries, with high sensitivity for detecting fractures while reducing unnecessary imaging. 1, 2
Ottawa Ankle Rules
The Ottawa Ankle Rules indicate that ankle radiographs are required only when patients with acute ankle injuries have:
- Pain in the malleolar zone AND either:
- Bone tenderness at the posterior edge or tip of the lateral malleolus, OR
- Bone tenderness at the posterior edge or tip of the medial malleolus, OR
- Inability to bear weight for four steps both immediately after injury and in the emergency department
Ottawa Foot Rules
For midfoot injuries, radiographs are required only when patients have:
- Pain in the midfoot zone AND either:
- Bone tenderness at the base of the fifth metatarsal, OR
- Bone tenderness at the navicular bone, OR
- Inability to bear weight for four steps both immediately after injury and in the emergency department
Ottawa Knee Rule
The Ottawa Knee Rule states that knee radiographs are only required when patients with acute knee injuries have any of the following:
- Age 55 years or older
- Isolated tenderness of the patella
- Tenderness at the head of the fibula
- Inability to flex the knee to 90 degrees
- Inability to bear weight for four steps both immediately after injury and in the emergency department 1, 2
Clinical Application and Performance
- Sensitivity: The Ottawa Rules demonstrate nearly 100% sensitivity for detecting clinically significant fractures 3, 4, 5
- Specificity: Moderate specificity (40-60%) 3, 4
- Reduction in radiography: Implementation can reduce unnecessary radiographs by approximately 30-35% 6, 3, 5
Important Exclusions and Limitations
The Ottawa Rules should NOT be applied in the following situations:
- Patients under 5 years of age 2
- Penetrating trauma
- Pregnancy
- Skin wounds
- Patients transferred with radiographs already taken
- Injuries >10 days old
- Return visits for continued traumatic pain
- Polytrauma
- Altered mental status
- Neurologic abnormalities affecting the extremity
- Underlying bone disease 1, 2
Special Considerations
- Age modifications: Some evidence suggests automatically ordering radiographs for all patients ≥65 years with ankle injuries, as this improves sensitivity to 99% 7
- Occult fractures: In patients with positive Ottawa Rules but negative radiographs who continue to have significant pain, consider advanced imaging such as 3D-CT, which may detect occult fractures 5
- Clinical judgment: While the Ottawa Rules are highly sensitive, clinical judgment remains paramount and should supersede these guidelines when there is strong clinical suspicion of fracture 1, 2
Implementation Tips
- For proper evaluation of acute knee injuries meeting Ottawa criteria, obtain at minimum two radiographic views: anteroposterior and lateral 1
- For ankle injuries, standard radiographs should include anteroposterior, lateral, and mortise views
- Document compliance with Ottawa Rules in clinical notes to justify imaging decisions 6