Inability to bear weight both immediately and in the emergency department (4 steps)
The Ottawa knee rules were derived to aid in the efficient use of radiography in acute knee injuries and have since been prospectively validated on multiple occasions in different populations and in both children and adults. Some studies found sensitivities for the Ottawa knee rules of 98-100% for clinically significant knee fractures, meaning if the patient is negative for all criteria, the patient is likely not to have a knee fracture. However, specificities for the Ottawa knee rules are typically poor, meaning a medical provider cannot say without proper testing what injury the patient may have. The Pittsburgh knee rules have been found to be more specific in diagnosis.
^Stiell IG, Wells GA, Hoag RH, Sivilotti ML, Cacciotti TF, Verbeek PR, Greenway KT, McDowell I, Cwinn AA, Greenberg GH, Nichol G, Michael JA. (1997). "Implementation of the Ottawa Knee Rule for the use of radiography in acute knee injuries.". JAMA278 (27): 2075–9. doi:10.1001/jama.1997.03550230051036. PMID9403421.
^Cheung TC, Tank Y, Breederveld RS, Tuinebreijer WE, de Lange-de Klerk ES, Derksen RJ. (2013). "Diagnostic accuracy and reproducibility of the Ottawa Knee Rule vs the Pittsburgh Decision Rule.". Am J Emerg Med.31 (4): 641–5. doi:10.1016/j.ajem.2012.11.003. PMID3399332.