Upright weight-bearing CT of the knee during flexion: changes of the patellofemoral and tibiofemoral articulations between 0° and 120°

  • Anna Hirschmann
  • Florian M. Buck
  • Ramin Herschel
  • Christian W. A. Pfirrmann
  • Sandro F. Fucentese



To prospectively compare patellofemoral and tibiofemoral articulations in the upright weight-bearing position with different degrees of flexion using CT in order to gain a more thorough understanding of the development of diseases of the knee joint in a physiological position.

Materials and methods

CT scans of the knee in 0°, 30°, 60° flexion in the upright weight-bearing position and in 120° flexion upright without weight-bearing were obtained of 10 volunteers (mean age 33.7 ± 6.1 years; range 24–41) using a cone-beam extremity-CT. Two independent readers quantified tibiofemoral and patellofemoral rotation, tibial tuberosity–trochlear groove distance (TTTG) and patellofemoral distance. Tibiofemoral contact points were assessed in relation to the anteroposterior distance of the tibial plateau. Significant differences between degrees of flexion were sought using Wilcoxon signed-rank test (P < 0.05).


With higher degrees of flexion, internal tibiofemoral rotation increased (0°/120° flexion; mean, 0.5° ± 4.5/22.4° ± 7.6); external patellofemoral rotation decreased (10.6° ± 7.6/1.6° ± 4.2); TTTG decreased (11.1 mm ±3.7/−2.4 mm ±6.4) and patellofemoral distance decreased (38.7 mm ±3.0/21.0 mm ±7.0). The CP shifted posterior, more pronounced laterally. Significant differences were found for all measurements at all degrees of flexion (P = 0.005–0.037), except between 30° and 60°. ICC was almost perfect (0.80–0.99), except for the assessment of the CP (0.20–0.96).


Knee joint articulations change significantly during flexion using upright weight-bearing CT. Progressive internal tibiofemoral rotation leads to a decrease in the TTTG and a posterior shift of the contact points in higher degrees of flexion. This elucidates patellar malalignment predominantly close to extension and meniscal tears commonly affecting the posterior horns.


Upright weight-bearing CT Weight-bearing knee joint alignment Patellofemoral Tibiofemoral Contact point 


Compliance with ethical standards

Conflict of interest

No potential conflicts of interest to disclose.


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Copyright information

© European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2015

Authors and Affiliations

  • Anna Hirschmann
    • 1
    • 3
  • Florian M. Buck
    • 1
  • Ramin Herschel
    • 2
  • Christian W. A. Pfirrmann
    • 1
  • Sandro F. Fucentese
    • 2
  1. 1.Department of Radiology, Orthopedic University Hospital BalgristUniversity of ZurichZurichSwitzerland
  2. 2.Department of Orthopedic Surgery, Orthopedic University Hospital BalgristUniversity of ZurichZurichSwitzerland
  3. 3.Clinic of Radiology and Nuclear MedicineUniversity of Basel HospitalBaselSwitzerland

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