Pittsburgh Knee Rules
Original Editor - Johnathan Fahrner
A clinical decision rule used to indicate the use of radiography of the knee following an injury.
Radiographs of the knee should performed if the mechanism of injury is a fall or blunt trauma and either one of the following:
1) Patient is younger than 12 or older than 50
2) Inability to walk four weight-bearing steps
These rules do not apply to individuals who present more than 6 days after injury, those with only superficial lacerations and abrasions, those with a previous history of knee injury or surgery on the affected knee, and those being reassessed for the same injury. 
In a study by Seaberg et al., of 934 patients evaluated the Pittsburgh knee rules applied to 745 with a sensitivity of 0.99 and a specificity of 0.60. There was the potential to reduce radiography by 52% with one missed fracture. 
In a more recent study by Cheung et al., the Pittsburgh knee rules had a pooled sensitivity of 0.86 and a pooled specificity of 0.51. 
Recommendations for Clinical Practice
The Pittsburgh knee rules are often compared to the Ottowa knee rules. While the Pittsburgh knee rules have a higher specificity, each have almost identical sensitivities.  The ability of these rules to rule out a condition, and thus avoid a radiograph is important and their most valuable characteristics. With proper training either set of rules could be adopted for use. 
- Hawley C, Rosenblatt R. Ottowa and Pittsburgh rules for acute knee injuries. The Journal of Family Practice 1998;47(4):254-255. http://www.ncbi.nlm.nih.gov/pubmed/9789509. (Accessed 25 Apr 2013).
- Seaberg DC, Yealy DM, Lukens T, Auble T, Mathias S. Multicenter comparison of two clinical decision rules for the use of radiography in acute, high-risk knee injuries. Annals of Emergency Medicine 1998;32(1):8-13. http://www.ncbi.nlm.nih.gov/pubmed/9656942. (Accessed 25 Apr 2013).
- Cheung TC, Tank Y, Breederveld RS, Tuinebreijer WE, de Lange-de Klerk ES, Derksen RJ. Diagnostic accuracy and reproducibility of the Ottawa Knee Rule vs the Pittsburgh Decision Rule. American Journal of Emergency Medicine 2013;31(4):641-5. http://www.ncbi.nlm.nih.gov/pubmed/23399332. (Accessed 25 Apr 2013).