Ottawa Knee Rule
Determines need for knee X-ray following acute knee injury
How to use & interpret
The Ottawa knee rule is a sensitive decision aid for whether an acute knee injury needs an X-ray, safely reducing imaging. A radiograph is indicated if any one of five is present: age ≥55, isolated tenderness of the patella, tenderness at the head of the fibula, inability to flex the knee to 90°, or inability to bear weight (four steps) both immediately and in the department.
Because it is designed to be highly sensitive (very few missed fractures) rather than specific, a 'positive' rule means image — it does not mean a fracture is present.
Score interpretation
All criteria absent — fracture effectively excluded
→ No X-ray required. RICE, analgesia, physiotherapy referral.
One or more criteria present — fracture cannot be excluded
→ Knee X-ray (AP and lateral)
Interpretation bands for the Ottawa Knee. Apply clinical judgement and local guidance.
Frequently asked questions
Does the Ottawa knee rule apply to children?
It is validated mainly in adults; apply cautiously in young children and where assessment is limited by swelling, distracting injury or reduced consciousness.
References
- Stiell IG, et al. Prospective validation of a decision rule for the use of radiography in acute knee injuries. JAMA. 1996;275(8):611–5.
Related
Curated clinical cross-links plus same-class fallbacks.
- Tranexamic Acid (ICU/Trauma/Surgical) · Antifibrinolytic
- Co-amoxiclav (Open Fracture Antibiotic Prophylaxis) · Beta-lactam / Beta-lactamase Inhibitor Combination
- Piperacillin-Tazobactam (Polymicrobial Open Fracture Infections) · Extended-spectrum Beta-lactam / Beta-lactamase Inhibitor
- Tranexamic Acid (Surgical / Trauma Haemorrhage) · Antifibrinolytic (Haemostatic)
- Difficult Airway Algorithm (DAS) · DAS 2015; Royal College of Anaesthetists
- Major Haemorrhage Protocol · NICE NG24; UK MHP guidelines
- New-Onset Atrial Fibrillation · ESC 2020 AF Guidelines; NICE NG196
- Hypertensive Emergency · ESC/ESH 2018 Hypertension Guidelines; NICE NG136
- Bradycardia Management · Resuscitation Council UK ABCDE; ESC 2021 Pacing Guidelines
- Ventricular Tachycardia / Fibrillation · Resuscitation Council UK ACLS; ESC 2022 Ventricular Arrhythmia Guidelines
Featured in these MRCEM clinical pathways
The Ottawa Knee is covered in detail — with RCEM/NICE evidence base, indications and pitfalls — in the following exam-focused pathways on our sister siteReviseMRCEM.
MRCEM Primary / Intermediate / OSCE candidates: each pathway includes exam-style questions, RCEM/NICE citations, and FAQ summaries.
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.