Ottawa Knee Rules
Determines need for radiography in acute knee injuries to reduce unnecessary X-rays
- Highest activation tier
- Mandatory
- How it is scored
- Scored in code; a stated value is compared only from the structured summary or a supplied value
- Scoring type
- classification
- Care settings
- Emergency department, Outpatient
When it activates
Scribeable activates a calculator from the encounter. The Ottawa Knee Rules can activate when the transcript or pasted chart context documents any of these:
- Knee injury evaluation
- Knee pain after trauma
- Knee swelling assessment
- Suspected knee fracture
- Knee effusion after trauma
A coded diagnosis can also activate it. ICD-10 prefixes carried by the registry: S83.
Note-type scope: it activates on notes whose subject resolves to emergency medicine, hospital medicine. A note that resolves to another subject does not carry it even when the clinician's specialty matches; a note with no resolvable subject (a generic consultation) falls back to the specialty match.
Inputs the note needs
5 inputs. Each is resolved from the transcript, the pasted chart context and charted labs; an input marked "asks you" is requested as a clarification when it is undocumented.
| Input | Type | Unit / options | Guidance |
|---|---|---|---|
| Age ≥55 years | age | ||
| Isolated tenderness of the patella (no other knee bone tenderness) | exam | ||
| Tenderness at head of fibula | exam | ||
| Inability to flex knee to 90° | exam | ||
| Inability to bear weight for 4 steps immediately and in ED | exam |
Scoring
X-ray indicated if ANY positive: (1) Age ≥55, (2) Isolated tenderness of patella, (3) Tenderness at head of fibula, (4) Inability to flex 90°, (5) Inability to bear weight 4 steps immediately and in ED. Score: 0 = no X-ray needed, 1 = X-ray indicated.
Interpretation
All criteria negative: No X-ray needed (sensitivity 98.5-100% for fractures). Any criterion positive: X-ray indicated. Rules applicable only to acute knee injuries (age >2, injury within 7 days).
Evidence
Sources carried in Scribeable's citation registry for this calculator; guideline version: Stiell IG et al. 1995.
- Stiell IG et al. Prospective validation of a decision rule for the use of radiography in acute knee injuriesStiell et al. (Ottawa Knee) 1995 · 1995 · Level I · link last verified 2026-03-28
How Scribeable handles it in the note
When an encounter activates the Ottawa Knee Rules at the mandatory tier, Scribeable resolves its inputs from the transcript, the pasted chart context and any charted labs, and asks you for a missing input you can supply before the note is finalised. Bedside-exam and separately ordered study values are not requested one input at a time; a calculator that carries a combined clarification question may still put that single question to you.
The score is computed in code from the resolved inputs, not recalled by the language model. A stated Ottawa Knee Rules value is compared against the computed one when the draft's structured summary carries it; a disagreement found there is flagged to the second drafting pass, which is instructed to correct the score and its interpretation, unless Scribeable has supplied the computed value to that pass, in which case the value the draft writes is checked against the supplied one and a detected difference is shown beside the note for you to adjudicate rather than silently rewritten.
Classified as a mandatory rule-out score: a missed result carries acute harm, so the activation filter never approves it on uncertainty.
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