The Pittsburgh Knee Rules are a clinical decision rule used after an acute knee injury to help clinicians decide when knee radiographs (X-rays) are indicated to look for fracture—and when imaging is often unnecessary. The rule is designed to be simple and highly sensitive for clinically important fractures, helping reduce avoidable X-rays and ED wait times. Medscape Reference+3AAFP+3PubMed+3
Core criteria (how the rule works)
The Pittsburgh rule is applied when the mechanism is blunt trauma or a fall. If that mechanism is present, order a knee X-ray if either:
- Age < 12 years or > 50 years, OR
- Inability to walk 4 weight-bearing steps in the ED/clinic. Medscape Reference+3Wikipedia+3AAFP+3
If the mechanism is blunt trauma/fall and neither criterion is present, a fracture is less likely and an X-ray is often unnecessary (clinical judgment still applies—especially with deformity, high-energy trauma, anticoagulation, concerning exam, etc.). AAFP+2Radiopaedia+2
Accuracy and comparison (quick context)
In a multicenter comparison study, the Pittsburgh rule showed very high sensitivity with better specificity than the Ottawa Knee Rule in that dataset—meaning it can reduce imaging while still being very good at not missing fractures. PubMed+2PMC+2
Pittsburgh Knee Rules – Knee X-ray Necessity Calculator
For acute knee injury. Uses the Pittsburgh Knee Rule logic (blunt trauma/fall + age criterion and/or inability to walk 4 steps).
Patient inputs
- Apply if: blunt trauma or fall
- X-ray if: age < 12 or > 50, or unable to walk 4 steps
