Menu

For healthcare professionals

Pittsburgh Knee Rule

The Pittsburgh knee rule helps decide which knee injuries from a fall or blunt trauma need an X-ray. It uses only age and whether the patient can walk four weight-bearing steps. Seaberg and Jackson published it in 1994. This tool is written for clinicians and is not a diagnosis.

Last reviewed: By the uncovermyrisk.com editorial team Educational only, not medical advice.

A leg that is cold, pale or numb below the knee, a badly misshapen knee, or bone through the skin: call 911 now.General safety advice (not part of the published rule). The rule is for patients already being assessed; it does not replace urgent care.

Patient findings

Nothing you enter leaves this page.

Does the rule apply?
Walking
Result appears here

What you will see

Whether the rule calls for a knee X-ray, and which finding triggered it.

Educational only, not medical advice. Not a diagnosis. Imaging decisions belong to the treating team.

Source

Seaberg DC and Jackson R, American Journal of Emergency Medicine 1994. The criteria are taken from the open-access (CC BY) introduction of Shrestha and Park, Cureus 2026, and match the wording in Lindor and colleagues, Clinical Practice and Cases in Emergency Medicine 2025 (CC BY). The tests check the age cut points, the walking item and that the rule only applies after a fall or blunt trauma.

Validated in

Patients of any age with a knee injury from a fall or blunt trauma. Other mechanisms, such as twisting injuries, are outside the rule (Shrestha 2026).

Limits

The rule is built to rule out fractures, not to find them: a positive result means an X-ray is indicated, not that a fracture is present. It is less widely validated than the Ottawa knee rule (Bradley 2022), and a case review warns that tibial plateau fractures can be subtle (Lindor 2025).

The rule

For a knee injury from a fall or blunt trauma, a knee X-ray is recommended if any one of the following is present (Shrestha 2026):

The same criteria are described by Lindor and colleagues (Lindor 2025). The rule was published by Seaberg and Jackson (Seaberg 1994).

Worked example: a 35-year-old who fell on a knee and can walk four steps without help meets no criterion, so the rule does not call for an X-ray. A 60-year-old with the same fall meets the age criterion, so the rule calls for an X-ray.

What the studies found

The original validation study reported a sensitivity of 100% and a specificity of 79% (Shrestha 2026). A review reports a sensitivity of 99% to 100% and a specificity of 60% to 80% across studies (Bradley 2022).

In a UK audit of 202 knee X-ray requests, 41 (20.3%) involved mechanisms outside a fall or blunt trauma, and no request documented enough information to show the rule was negative (Shrestha 2026).

Related calculators

For a five-item knee rule, see the Ottawa Knee Rule. For ankle and midfoot injuries, see the Ottawa Ankle Rules. Other bedside scores are listed under For healthcare professionals.

Sources

  1. Shrestha P, Park JY. Adequacy of Clinical Information in Knee Radiography Requests With Reference to the Pittsburgh Knee Rule: A Single-Centre Clinical Audit. Cureus. 2026;18(9):e116695. doi:10.7759/cureus.116695. PMID 42923598. Open access (CC BY 4.0). Introduction: the Pittsburgh knee rule criteria; original validation sensitivity 100%, specificity 79%; 202 requests, 41 (20.3%) not applicable. pmc.ncbi.nlm.nih.gov/articles/PMC13687817/
  2. Lindor R, Ghaith S, Newberry J, Thomas A. Medical and Legal Risks in Tibial Plateau Fractures. Clin Pract Cases Emerg Med. 2025;9(3):255-258. doi:10.5811/cpcem.38452. PMID 42456294. Open access (CC BY 4.0). Pittsburgh knee rule criteria; tibial plateau fractures can be subtle. pmc.ncbi.nlm.nih.gov/articles/PMC12342674/
  3. Bradley AT, Adler JA, Curtis DM, et al. Are Oblique Views Necessary? A Review of the Clinical Value of Oblique Knee Radiographs in the Acute Setting. West J Emerg Med. 2022;23(6):939-946. doi:10.5811/westjem.2022.8.56453. PMID 36409955. Open access (CC BY 4.0). Pittsburgh knee rules less widely validated; sensitivity 99% to 100%, specificity 60% to 80%. pmc.ncbi.nlm.nih.gov/articles/PMC9683766/
  4. Seaberg DC, Jackson R. Clinical decision rule for knee radiographs. Am J Emerg Med. 1994;12(5):541-543. doi:10.1016/0735-6757(94)90274-7. PMID 8060409. Original paper (cited; the criteria used here are taken from Shrestha 2026, CC BY). pubmed.ncbi.nlm.nih.gov/8060409/

Written and maintained by the uncovermyrisk.com editorial team. We do not have a medical reviewer; every claim links to its primary source above. Last reviewed: 2026-11-02. Spotted an error? See About.