**5. Conclusions**

Non-contact ACL injury was associated with age, passive knee extension and weak hamstring knee strength in an ACL reconstruction population whatever gender. Passive knee valgus is strongly associated with the female population. Unfortunately, all these factors are not changeable. Only hamstring isokinetic strength could be improved by strengthening. These modifiable intrinsic factors are also associated with different subpopulations particularly in men, but also in young athletes under 23.5 years old and in populations with an anteroposterior knee laxity upper 4.5 mm. According to these results, hamstring strengthening could be achieved especially in these populations. However, this preventive attitude needs to be confirmed by prospective comparative studies in future.

**Author Contributions:** Conceptualization, M.D. and A.F.-C.; formal analysis, M.D.; investigation, M.D., J.G., P.M., V.C., B.L. and A.F.-C.; methodology, A.F.-C. and M.D.; project administration, A.F.-C.; resources, M.D.; software, M.D.; supervision, A.F.-C.; validation, P.M.; writing—original draft, M.D. and A.F.-C.; writing—review and editing, A.F.-C., P.M., V.C., B.L., J.G., and M.D. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** The study was performed according to the World Medical Association Declaration of Helsinki and according to the French legislation (articles L.1121-1 paragraph 1 and R1121-2, Public health code), with the agreement of the local Ethics Committee (Groupe Nantais d'Ethique dans le Domaine de la Santé (GNEDS)) on 19 February 2020.

**Informed Consent Statement:** The patients gave their written consent to participate in the study.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to ethical reasons.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

