The Pittsburgh knee rules are medical rules created to ascertain whether a knee injury requires the use of X-ray

Radiology

Radiology is a medical specialty that employs the use of imaging to both diagnose and treat disease visualized within the human body. Radiologists use an array of imaging technologies to diagnose or treat diseases...

 to assess a fracture

Fracture

A fracture is the separation of an object or material into two, or more, pieces under the action of stress.The word fracture is often applied to bones of living creatures , or to crystals or crystalline materials, such as gemstones or metal...

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Criteria

• Blunt trauma
  Blunt trauma
  In medical terminology, blunt trauma, blunt injury, non-penetrating trauma or blunt force trauma refers to a type of physical trauma caused to a body part, either by impact, injury or physical attack; the latter usually being referred to as blunt force trauma...
  
  or a fall as mechanism of injury AND either of the following
  • Age younger than 12 years or older than 50 years
  • Inability to walk four weight-bearing steps in the emergency department.

If the patient satisfies the above criteria, they should receive an X-ray to assess for a possible fracture.

Accuracy

The sensitivity of using the Pittsburgh Knee rules is 99% with a specificity of 60%. That means the use of the above rules has a false negative result of 1% and a false positive result of 40%.

The false positive result is less important as if the patient is positive, they should receive an Xray to assess for a possible fracture which has a much higher specificity.

The use of the Pittsburgh Knee rules reduces the use of knee radiographs by 52%.