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Comparable accuracy of femoral joint line reconstruction in different kinematic and functional alignment techniques



A key part of kinematic alignment (KA) and functional alignment (FA) is to restore the natural femoral joint line, in particular the medial joint line. KA is known to reproduce the femoral joint line accurately; however, direct comparisons with other surgical techniques such as FA are currently lacking. The purpose of this study was to evaluate differences of alignment parameters in KA and FA techniques with a special focus given to the femoral joint line.


We performed a retrospective radiological analysis of pre- and postoperative long leg radiographs of 221 consecutive patients with varus or neutral leg alignment, who underwent primary total knee arthroplasty (TKA) procedures from 2018 to 2020. Patients were assigned to one of four groups: (1) FA: image-based robotic-assisted TKA, (2) FA: imageless robotic-assisted TKA, (3): restricted KA: 3D cutting block-assisted (patient-specific instruments, PSI) TKA, (4): unrestricted KA: calipered technique. Patients’ radiographs were (re)-analyzed for overall limb alignment, medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), as well as medial and lateral femoral joint line alteration. Statistical significance was determined using unpaired t testing (FA vs. KA group) and one-way ANOVA (subgroup analyses).


Comparisons of KA vs. FA, as well as individual subgroups of KA and FA did not show any differences in the accuracy of medial joint line reconstruction (< 2 mm, p = 0.384, p = 0.744, respectively) and LDFA alteration (< 2°, p = 0.997, 0.921, respectively). Correction of MPTA (3.4° vs. 2.2°) and lateral femoral joint line (2.1 mm vs. 1.5 mm) was higher for FA and FA subgroups compared to KA and KA subgroups (both p < 0.001).


Kinematic and functional alignments showed a comparable accuracy in reconstruction of the medial femoral joint line and femoral joint line orientation. Increased correction of MPTA and lateral femoral joint line was recorded with FA techniques.

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Fig. 3

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.



Arithmetic hip-to-knee angle


Adductor tubercle


Adductor tubercle joint line distance


Bi-cruciate stabilized


Computed tomography


Functional alignment


Hip-to-knee angle


Joint line


Joint line obliquity


Kinematic alignment


Lateral distal femoral angle


Lateral femoral joint line


Medial femoral joint line


Medial proximal tibial angle


Overall limb alignment


Patient-specific instruments


Posterior stabilized


Robotic-assisted total knee arthroplasty


Standard deviation


Total knee arthroplasty


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We thank Felix KF Kommoss for English language editing of the current manuscript.


This research received no external funding.

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Authors and Affiliations



Conceptualization, L-RT, PS, HW and ME; data curation, MZ, L-RT, PS; formal analysis, L-RT, HW and ME; investigation, MZ, L-RT, PS; methodology, L-RT, MZ, PS, HW and ME; project administration, HW and ME; supervision, ME; visualization, PS; writing—original draft, L-RT; writing—review and editing, PS, DJ, HW and ME.

Corresponding author

Correspondence to Lars-Rene Tuecking.

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Conflict of interest

LT, PS, ME and HW are paid educational consultants for Stryker. LT, PS and ME are paid educational consultants for Smith & Nephew. HW is a paid consultant for Medacta. No funding was received for this study. MZ and DJ have no conflict of interest.

Ethical approval

This study was approved by the local ethics committee (8403_BO_S_2019).

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Informed consent was not needed due to the use of only anonymized data (radiographs) in this retrospective study.

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Tuecking, LR., Savov, P., Zander, M. et al. Comparable accuracy of femoral joint line reconstruction in different kinematic and functional alignment techniques. Knee Surg Sports Traumatol Arthrosc (2023).

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  • Kinematic alignment
  • Functional alignment
  • Robotic TKA
  • RA-TKA
  • PSI
  • Unrestricted KA
  • Joint line
  • Accuracy
  • Total knee arthroplasty