Q Angle

Other Names

Measurement of the Q angle

Measurement of the Q angle. ASIS – anterior superior iliac spine; CP-centre of patella; TT-tibial tuberosity; Q- quadriceps angle

• Q Angle
• Quadriceps angle

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Purpose

• Definition: angle formed by a line representing the femoral shaft to the patella and the ischial tuberosity to the patella
• Purpose: evaluate the effect of the quadriceps muscles on the patellofemoral joint biomechanics
• Normal values
  • Women: should be less than 22° in extension, less than 9° in flexion
  • Men: Should be less than 18° in extension, less than 8° degrees in flexion
  • Study: mean 14.8°, +/- 5.4°

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Description

• Can be measured in the standing or supine position
• Standing may be more appropriate given weightbearing better reflects the biomechanics of the knee
• Historically, Q angle measured with knee in full extension
• When the knee is flexed, the tibia rotates medially relative to the femur, reducing the Q angle

Measurement

• Place the hip/knee/foot in a neutral position
• Draw a line from ASIS to the midpoint of the patella
• Draw another line from the tibial tubercle to the patella
• The resultant angle is the Q angle

Abnormal Findings

• Normal: females 13-18°, males 12-15°
• Values greater or lesser than these are considered abnormal

Problems with measurement

• Estimate of line of pull, may not accurately reflect biomechanics of the quadriceps muscle
• Muscle imbalances in the quads can lead to incorrect estimates on the forces
• If the patella is sitting abnormally, it can provide a falsely abnormal Q angle

Factors Affecting Q Angle

• Femoral anteversion
• External tibial torsion
• Laterally displaced tibial tubercle
• Genu valgum
• Quadricep Contraction
• Height, Age and Gender

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Pathology

• Patellofemoral Pain Syndrome
• Genu Valgum
• Genu Varum
• Genu Recurvatum

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Evidence

• Needs to be updated

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See Also

• Knee Pain Main
• Physical Exam Knee
• Knee Anatomy Main

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