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Lower Extremity Alignment

  Mechanical axis of Lower extremity  Mechanical axis of Lower extremity
  • line drawn from center of femoral head to center of ankle joint,
  • should pass through center of knee.
Mechanical Axis Measurements Mechanical Axis Measurements
  • LDFA = lateral distal-femoral angle
    -angle between mechanical axis of femur and the articular surface of the distal femure
    -Normal 87°
  • MPTA = medial proximal tibial angle
    -angle between tibial mechanical axis and the articular surface of the proximal tibia
    -Normal = 87°
  • LDTA = lateral distal tibial angle
    -angle between tibial mechanical axis and the distal tibial articular surface
    -Normal =90°
  1. Femoral mechanical axis
  2. Tibial mechanical axis
Average Anatomic Joint Line Measurements Average Anatomic Joint Line Measurements
  • Proximal femoral angle = 84°
  • Lateral distal femoral anatomic angle = 81°
  • Medial proximal tibial anatomic angle = 87°
  • Distal tibial anatomic angle = 90°

(Price CT, Orthopaedics 2005;28:20)