1 Before you use it
What it is
Five criteria for an acute knee injury. Image if any are present: age 55 or over · isolated patellar tenderness · tenderness at the head of the fibula · inability to flex to 90° · inability to weight-bear four steps immediately and in the department.
When to reach for it
Every acute knee injury. It runs in the same minute as the effusion sweep test and the extension check — and those two are doing separate work: the rule answers does this need a film, the effusion answers what is going on inside the joint.
2 Giving it
Scoring
Not scored. Any one criterion positive → x-ray. All five negative → the rule says imaging is not indicated.
Isolated patellar tenderness means tenderness at the patella and nowhere else — a detail students routinely miss, and it changes the answer.
What it doesn’t measure
Anything about ligament or meniscal injury. A negative rule does not clear the ACL. On a knee that swelled within an hour, the rule can be negative and the ACL still ruptured — test it.
Pair it with: Lachman and the meniscal tests, IKDC or KOOS for baseline function, and ACL-RSI later if you are heading toward return to sport.
3 Reading the score
Interpreting it
Same logic as the ankle rules: a sensitive rule-out. A negative rule makes a clinically significant fracture unlikely. A positive rule is not a diagnosis, it is a request for a film.
No verified accuracy figure is carried in our library, and none is printed here.
Where it does not apply: under 18, isolated superficial injury, altered conscious state, paraplegia, or multiple injuries.
Is the change real?
Student trap. Treating a negative rule as "the knee is fine". It rules out a fracture, not a rupture.
Official source: aci.health.nsw.gov.au. We don't host the form.
This is a learning tool. It does not diagnose patients and does not replace your clinical educator.
Did this page do its job?
CliniStudy is in beta. One tap is enough — it decides what gets fixed first.