The aim of this study was to analyze the coronal alignment of a large population of patients undergoing total knee arthroplasty using a modern classification of the knee phenotypes found in a population of non-osteoarthritic patients.

Methods Five hundred and four navigated total knee arthroplasties will be analyzed. The following angles will be measured with a computer image free navigation system: medial femorotibial mechanical angle without stress and with maximum manual stress to reduce deformation, and medial distal femoral mechanical angle. The native medial distal femoral and medial proximal tibial angles will be calculated. The data will be analyzed as numerical and categorical data. These data will be then compared with those published in a non-arthritic population, considered as a control group.

The main criterion will be the percentage of subjects with normal overall coronal alignment, defined by the association of a normal native medial distal femoral angle and a normal native medial proximal tibial angle. The secondary criteria will be the percentages of subjects with normal medial femorotibial mechanical angle, normal native medial distal femoral angle and normal native medial proximal tibial angle. The influence of gender on primary and secondary criteria in the study group will be analyzed. The most frequent phenotypes in the study group will be identified.

Inclusion criteria:

• Patient aged ≥ 18 years
• Patient operated between 01/01/2011 to 02/28/2021 by two experienced surgeons of a total knee prosthesis using a navigation system without image (OrthoPilot ®, Aesculap, Tuttlingen, FRG) allowing to measure during the intervention the anatomical parameters of the subject before implantation;
• Records including a complete intraoperative anatomical analysis;
• Subject who has not expressed his opposition, after being informed, to the reuse of his data for the purposes of this research.

Exclusion criteria:

• Subject who expressed their opposition to participating in the study
• Impossibility of giving the subject informed information (difficulties in understanding the subject, etc.)
• Incomplete or absent anatomical analysis
• Subject under guardianship, curatorship or safeguard of justice

Patient aged ≥ 18 years operated between 01/01/2011 to 02/28/2021 by two experienced surgeons of a total knee prosthesis using a navigation system without image (OrthoPilot ®, Aesculap, Tuttlingen, FRG) allowing to measure during the intervention the anatomical parameters of the subject before implantation;