The Pittsburgh knee rules are medical rules created to ascertain whether a

knee injury In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...

requires the use of an

X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

to assess a

fracture Fracture is the appearance of a crack or complete separation of an object or material into two or more pieces under the action of stress (mechanics), stress. The fracture of a solid usually occurs due to the development of certain displacemen ...

Criteria

Blunt trauma A blunt trauma, also known as a blunt force trauma or non-penetrating trauma, is a physical trauma due to a forceful impact without penetration of the body's surface. Blunt trauma stands in contrast with penetrating trauma, which occurs when a ...

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 In orthopedics, weight-bearing is the amount of weight a patient puts on an injured body part. Generally, it refers to a leg, ankle or foot that has been Bone fracture, fractured or upon which surgery has been performed, but the term can also be us ...

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 A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test resu ...

result of 1% and a

false positive A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test resu ...

result of 40%. From a medical point of view, the false positive result is less important as if the patient is positive, they should receive an X-ray to assess for a possible fracture, which has a much higher specificity. However, from a practical point of view, false positives that lead to negative X-ray tests were the very thing that the knee rules are trying to address. Nonetheless, the Pittsburgh knee rules offer fewer false positives than do the Ottawa knee rules, though the Ottawa knee rules are more commonly used. The Ottawa knee rules count even a limping step as a step. Pittsburgh counts only a complete heel/toe plant as a step. This key difference likely accounts for the difference in specificity. The use of the Pittsburgh knee rules reduces the use of knee

radiographs Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical ("diagnostic" radiography and "therapeu ...

by 52%.

References

{{Bone, cartilage, and joint procedures Diagnostic emergency medicine Examination of the knee Orthopedic clinical prediction rules

Criteria

Accuracy

See also

References