Ipsilateral patellofemoral morphological abnormalities are more severe than those of contralateral joints in patients with unilateral patellar dislocation



To determine the differences in anatomic parameters between ipsilateral dislocated knees and contralateral non-dislocated knees in patients with unilateral patellar dislocation and to identify any variations in ipsilateral knees contributing to contralateral anatomic abnormalities.


A total of 82 patients with unilateral patellar dislocation from 2016 to 2019 were retrospectively evaluated. Bilateral anatomic factors, including the tibial tubercle to trochlear groove (TT-TG) distance, lower limb rotational deformities, trochlear dysplasia, patella tilt, and patellar height, were assessed by CT.


The study included 46 patients (32 females and 14 males, mean age ± SD 20.5 ± 6.8). The interobserver reliability of each parameter showed excellent agreement. The ipsilateral TT-TG distance (P = 0.004), patella tilt (P = 0.001), and patellar height (P = 0.01) were greater in the ipsilateral knees than in the contralateral knees. The lateral trochlea inclination (LTI) in the contralateral knees was larger than that in the ipsilateral knees (P = 0.022). There was a significant difference in the distribution of trochlear dysplasia of Dejour between the ipsilateral knees (dislocated side) and the contralateral knees (P = 0.036). However, bilateral femoral and/or tibial torsion, and bilateral knee joint rotation did not differ significantly. Binary logistic regression showed that only ipsilateral LTI revealed significant ORs of 8.83 (P = 0.016) and 7.64 (P = 0.018) with regard to contralateral abnormal tibial torsion and LTI, respectively.


In patients with unilateral patellar dislocation, the ipsilateral TT-TG distance, patella tilt, and patellar height values were larger in the ipsilateral knees than in the contralateral knees, and trochlear dysplasia was more severe in the ipsilateral joints. The risks of contralateral pathological tibial torsion and LTI were 8.8- and 7.6-fold higher, respectively, in patients with abnormal ipsilateral LTI.

Level of evidence

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The authors did not receive support from any organization for the submitted work.

Author information




All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by PZ, LY and ZX. The first draft of the manuscript was written by JC, and modified by XH. HZ and AZ provided theoretical supports and retrospectively verify the diagnosis of unilateral patellar dislocation of all patients. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

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Correspondence to Aiguo Zhou.

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The authors declare they have no financial interests.

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the Ethics Committee of the First Affiliated Hospital of Chongqing Medical University. (Number: 2019–228).

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The informed consent was waived by the Ethics Committee of the First Affiliated Hospital of Chongqing Medical University in view of the retrospective nature of the study.

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Chen, J., Huang, X., Xu, Z. et al. Ipsilateral patellofemoral morphological abnormalities are more severe than those of contralateral joints in patients with unilateral patellar dislocation. Knee Surg Sports Traumatol Arthrosc (2021). https://doi.org/10.1007/s00167-021-06539-2

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  • Patellar dislocation
  • Patella alta
  • TT-TG distance
  • Trochlear dysplasia