Ottawa knee rule test is recommended for ruling out knee fractures in acute knee injury in adults.
A systematic review 1 on the accuracy of the Ottawa knee rule (OKR) to detect fractures in patients with acute knee injuries, including 11 prospective studies with a total of 5 986 patients, was abstracted in DARE. Six studies, with a total of 4 249 adult patients, were included in the pooled analysis. Four were classed as high quality, one as intermediate and one as low quality.
Five of the six studies included in the meta-analysis had a sensitivity of 100% for the detection of fractures. Of the 4 249 patients, 5 (0.12%) had a false-negative result on the OKR test. The pooled sensitivity was 98.5% (95% CI 93 to 100) and the pooled specificity was 49% (95% CI 43 to 51). The pooled negative LR was 0.05 (95% CI 0.02 to 0.23). The probability of a fracture after a negative test result, assuming a fracture prevalence of 7%, was 0.37% (95% CI 0.15 to 1.48).
The study that assessed children only (n=234, age range 2 to 18 years) reported a sensitivity of 92% (95% CI 64 to 100), a specificity of 50% (95% CI 42 to 56) and a probability of a fracture after a negative test result of 2% (95% CI 0.3 to 12).
According to the Ottawa knee rule, a knee radiograph series is required only for patients with knee injury who have any of these findings: 1) age 55 years or older; 2) isolated tenderness of patella (no bone tenderness of knee other than patella); 3) tenderness at head of fibula; 4) inability to flex 90 degrees; or 5) inability to bear weight both immediately and in the emergency department for 4 steps (unable to transfer weight twice onto each lower limb regardless of limping).
Blunt injuries, i.e. blows and falls, account for only 25% of all knee injuries, but they are responsible for more than 80% of all knee fractures. All but 3 of the studies included patients without distinguishing between the underlying mechanisms. Accuracy measures within more homogeneous subgroups classified according to the mechanism of injury would probably be somewhat different.
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