The number of prior knee arthroscopies is associated with an incremental increase in risk of revision in a subsequent total knee arthroplasty.

Purpose: The aim of this study was to estimate the relative risk of revision for total knee arthroplasty (TKA) with prior knee arthroplasties compared to TKAs in knees without prior surgery. In addition, this study aimed to assess if there was a dose-response relationship between the number of prior knee arthroscopies and the risk of TKA revision.

Methods: A retrospective observational study of three Danish Health Registries. All primary TKAs performed in Denmark from 1998 to 2021 were identified. Knee arthroscopies prior to primary arthroplasty were identified for these knees. The patients were grouped by whether they had an arthroscopy prior to the TKA or not. Kaplan-Meier analysis and Cox regression analysis was used to estimate implant survival and hazard ratio (HR) for revision.

Results: The study included 96,781 primary TKAs without prior surgery (de novo TKA) and 15,042 primary TKAs that had had one or more arthroscopies as only prior surgery. After adjusting for age, sex, and Charlson Comorbidity Index (CCI) the HR for revision was 1.38 (95% confidence interval [CI] 1.29-1.47, p < 0.001) for knees with prior arthroscopy compared to knees without prior arthroscopy. After adjusting for age, sex, and CCI each additional arthroscopy increased the HR for revision of 1.27 (95% CI 1.21-1.33, p < 0.001) in a dose-response manner.

Conclusion: Previous knee arthroscopies increase the risk of revision following primary TKA. More importantly, each additional knee arthroscopy increased the risk by 27%. Although the exact mechanism behind the observation is unknown, this is important information for both surgeons and patients when considering treatment options for knees affected by degenerative conditions.

Level of evidence: Level III, retrospective comparative study.