Orthopedics Book


Knee XRay Indications in Acute Injury

Aka: Knee XRay Indications in Acute Injury, Ottawa Knee Rule, Pittsburgh Knee Rules
  1. Epidemiology
    1. Fractures occur in only 6% of knee Trauma cases
  2. Indications
    1. Acute Knee Injury
      1. Ottawa Ankle Rules are validated for age 2 years old and older
  3. Efficacy: Accuracy for Acute Knee XRay Indications
    1. Pittsburgh Knee Rules (Pittsburgh Decision Rules)
      1. Test Sensitivity: 99%
      2. Test Specificity: 60%
      3. Reduced the use of Knee XRays by 52%
    2. Ottawa Knee Rules
      1. Test Sensitivity: 97%
      2. Test Specificity: 27%
      3. Reduced the use of Knee XRays by 28%
      4. Pretest probability determines likelihood of Fracture based on positive Ottawa Knee Rules
        1. Emergency Department (11% pretest probability)
          1. Ottawa Knee Rules positive: 20% chance of Fracture
          2. Ottawa Knee Rules negative: 1% chance of Fracture
        2. Clinic setting (2% pretest probability)
          1. Ottawa Knee Rules negative: Very low chance of Fracture
      5. References
        1. Bachmann (2004) Ann Intern Med 140(2):121-4 [PubMed]
  4. Indications: Pittsburgh Knee Rules (acute)
    1. Primary criteria (required)
      1. Blunt Trauma or fall type injury
    2. Secondary criteria (one of the following present)
      1. Age younger than 12 years or over 50 years
      2. Inability to walk four weight bearing steps in ER
  5. Indications: Ottawa Knee Rules (acute)
    1. Age over 55 years
    2. Isolated Patella bony tenderness
    3. Tenderness at head of fibula
    4. Inability to flex knee to 90 degrees
    5. Inability to bear weight (4 steps) - unable to transfer weight twice
      1. Immediately at site of accident
      2. Emergency department
    6. Rules efficacious down to age 5 years
      1. Bulloch (2003) Ann Emerg Med 42:48-55 [PubMed]
  6. References
    1. Stiell (1997) JAMA 278(23): 2076 [PubMed]
    2. Tandeter (1999) Am Fam Physician 60(9): 2599-608 [PubMed]

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