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Calculator · Does this knee need an X-ray?
Ottawa knee rule
Five criteria, any one of which means image. Applies to acute blunt knee injury in adults.
What it asks
| Criterion | Points |
|---|---|
| Age 55 or over | No — 0 Yes — 1 |
| Isolated tenderness of the patella No other bone tenderness | No — 0 Yes — 1 |
| Tenderness at the head of the fibula | No — 0 Yes — 1 |
| Unable to flex to 90° | No — 0 Yes — 1 |
| Unable to weight-bear 4 steps, both immediately and now | No — 0 Yes — 1 |
How to read the score
| Score | Means | What to do |
|---|---|---|
| 0 | No X-ray indicated | All five negative. Safe to treat without imaging in an alert, cooperative adult. |
| 1–5 | X-ray indicated | At least one positive. |
Before you use it
A negative rule excludes a FRACTURE, not an injury — the ligament and meniscal injuries that actually disable people are invisible on the film either way, so a normal X-ray is not a discharge summary. Same exclusions as the ankle rule: intoxication, distracting injury, reduced sensation.
Source: Stiell et al, Ann Emerg Med 1995
Checked, and shown
Every threshold on this page was checked against its primary source by a practising doctor. Here is what that involved, and what it found.