Knee Surgery, Sports Traumatology, Arthroscopy

, Volume 26, Issue 12, pp 3566–3571 | Cite as

Tibial tubercle–trochlear groove distance and angle are higher in children with patellar instability

  • Ilhan A. BayhanEmail author
  • Akay Kirat
  • Yakup Alpay
  • Baris Ozkul
  • Deniz Kargin



The purpose of this study was to assess the variations in tibial tubercle–trochlear groove distance and angle as a function of age and gender in a population of children without patellar instability (PI) compared with those with PI.


A retrospective review of 869 children’s knee MRIs, ages 5 to 15 years, were evaluated using a control group (792 children) without evidence of PI and a group with PI (77 children). Tibial tubercle–trochlear groove distance (TT–TGd) and angle (TT–TGa) were measured twice by two readers to assess intra- and inter-observer reliability and compared between PI and control groups. In both groups, functions of age and gender on TT–TGd and TT–TGa values were evaluated.


Both TT–TGd and TT–TGa measurements showed excellent intra- and inter-observer reliability. The mean TT–TGd for the PI group was 17.2 mm (SD 6.6) and significantly higher than the mean TT–TGd for the control group (10.4 SD 3.8 mm, P = 0.001). The mean TT–TGa for the PI was 20.8° (SD 8.3°), which was also significantly higher than the mean TT–TGa for the control group (12.5° SD 4.6°, P < 0.001). Control group revealed a positive correlation between age and TT–TGd measurements (r = 0.243, P < 0.001). The mean TT–TGa for girls (13.3° SD 4.7°) was higher than the mean TT–TGa for boys (11.9° SD 4.4°) in the control group (P < 0.001).


TT–TGa and TT–TGd are reliable and can be used for the evaluation of the extansor mechanism alignment in children with and without PI. However, it must be considered that TT–TGd is increasing in growing patients. Soft-tissue procedures may be prone to failure, since bony procedures for patellar alignment cannot be done until skeletal maturity.

Level of evidence



Patellar dislocation Patellar instability Risk factor Tibial–trochlear groove TT–TG Patellofemoral MRI 



No funding has been received for this study.

Compliance with ethical standards

Conflict of interest

The authors have no conflict of interest.

Ethical approval

This study was approved by Baltalimani Bone Diseases Education and Research Hospital Institutional Review Board (03.08.2017/12).

Informed consent

Informed consent was waived, because the study was a retrospective cross-sectional review.


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Copyright information

© European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2018

Authors and Affiliations

  • Ilhan A. Bayhan
    • 1
    Email author
  • Akay Kirat
    • 1
  • Yakup Alpay
    • 1
  • Baris Ozkul
    • 1
  • Deniz Kargin
    • 1
  1. 1.Department of OrthopedicsHealth Science University Baltalimani Bone Diseases Education and Research HospitalIstanbulTurkey

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