Should plain X-rays be routinely performed after blunt knee trauma? A prospective analysis.

Background: We tested the hypothesis that it was possible to decrease the number of performed x-rays after a knee trauma without delayed fracture diagnosis by using the Ottawa knee rules.

Methods: Patients had routine x-rays of the injured knee during the first stage of the study and selective x-rays during the second stage. All patients were followed up to 6 months after the trauma.

Results: 138 patients were included in the first stage; 57 had negative Ottawa criteria: no fracture was observed; following the Ottawa rules, 41% of the x-rays could have been avoided. 178 patients were included in the second stage; 63 patients had negative Ottawa criteria: no fracture was diagnosed during the whole follow-up; 35% of the x-rays have been avoided.

Conclusions: Ottawa rules allowed decreasing the number of x-rays performed after a knee trauma by 35% with a sensitivity for a knee fracture detection of 100%.