Rotational Alignment

  • Mechanical causes are present 30–50% of the time in cases of early failure, with specific causes including:
    • patellofemoral maltracking,
    • instability,
    • stiffness
    • malalignment of components
  • Rotational profile has an impact on
    • flexion gap
    • stability in flexion
    • patellofemoral
    • tibiofemoral joint kinematics
  • Malrotation may lead to problems
    • cam-shaft impingement
    • altered polyethylene loading and wear
    • patellar subluxation, dislocation
    • loosening
  • internal rotation of the femoral component
    • leads to
      • malalignment of the trochlear groove relative to the patella.
      • flexion gap asymmetry with a medial smaller flexion gap
        • causing an imbalance in soft tissues with increased tightness of the medial-sided structures and lateral-sided laxity.
  • Internal rotation of the tibial component
    • leads to
      • relative external rotation of the tibia and tubercle
        • causing an increased Q angle

Femoral Component

  • External rotation of the femoral component leads to a rectangular flexion space when the tibia is resected at 90 degrees relative to its anatomic axis
  • Options
    • transepicondylar axis
      • medial sulcus to the lateral epicondyle
    • Whiteside line
      • lowest point in the sulcus of the distal femur to the centre of the intercondylar notch
    • posterior condylar axis
      • varies with the difference in cartilage thickness between the medial and lateral condyles
    • gap technique

Tibial Component

  • Options
    • flexion gap symmetry,
    • posterior border of the tibia,
    • intermalleolar axis of the ankle,
    • largest mediolateral dimension of the tibia,
    • floating-knee trial
    • tibial tubercle
      • Align the AP axis of the tibial baseplate with the middle of the tibial tubercle

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.