Q Angle and Patellar Instability

Q Angle and Patellar Instability

Epidemiology of Patellar Instability : 

  • Most commonly occurs in 2nd-3rd decades of life
  • Risk factors include
    • Ligamentous laxity (Ehlers-Danlos syndrome)
    • Dysplastic vastus medialis oblique (VMO) muscle
    • Lateral displacement of patella
    • Patella alta
      • causes patella to not articulate with sulcus, losing its constraint effects
    • Trochlear dysplasia
    • Excessive lateral patellar tilt (measured in extension)
    • Lateral femoral condyle hypoplasia
    • Increased quadriceps angle (Q angle)
      • average for women 15 degrees
      • average for men 10 degrees
    • Previous patellar instability event
    • “Miserable malalignment syndrome” 
      •  A term named for the 3 anatomic characteristics that lead to an increased Q angle :
        • femoral anteversion
        • genu valgum
        • external tibial torsion / pronated feet

About the author: Dr. Tushar Mehta

An Orthopaedic Surgeon who is a blend of academic excellence and entrepreneurship with interest in all aspects of Bones and Joints. contach him at [email protected]

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