**5. Conclusions**

Preoperative TKA could be a benefit for in proper correction of sagittal spinopelvic alignment by spinal fusion. Therefore, preoperative TKA could be considered a preceding surgical option for patients with severe sagittal spinopelvic parameters in concurrent KOA and degenerative LSD.

**Author Contributions:** Conceptualization, H.J.K., J.H.Y. and D.-G.C.; methodology, H.J.K., J.H.Y. and S.W.S.; validation, H.J.K., J.H.Y., S.-I.K., K.-S.S. and W.C.; investigation, H.J.K.; data curation, H.J.K. and H.J.; writing—original draft preparation, H.J.K., J.H.Y. and D.-G.C.; writing—review and editing, H.J.K., J.H.Y. and D.-G.C.; visualization, J.H.Y. and S.W.S.; supervision, D.-G.C.; project administration, D.-G.C. 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 conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board of of Inje University Sanggye Paik Hospital (IRB number: 2021-03-012).

**Informed Consent Statement:** Patient consent was waived due to retrospective design.

**Data Availability Statement:** Data collected for this study, including individual patient data, will not be made available.

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