Background The optimal timing to perform a total knee arthroplasty (TKA) after knee arthroscopy (KA) was controversial in the literature. We aimed to 1) explore the effect of prior KA on the subsequent TKA; 2) identify who were not suitable for TKA in patients with prior KA, and 3) determine the timing of TKA following prior KA. Methods We retrospectively reviewed 87 TKAs with prior KA and 174 controls using propensity score matching in our institution. The minimum follow-up was 2 years. Postoperative clinical outcomes were compared between groups. Kaplan-Meier curves were created with reoperation as an endpoint. Multivariate Cox proportional hazards regressions were performed to identify risk factors of severe complications in the KA group. The two-piecewise linear regression analysis was performed to examine the optimal timing of TKA following prior KA. Results The all-cause reoperation, revision, and complication rates of the KA group were significantly higher than those of the control group (p < 0.05). The survivorship of the KA group and control group was 92.0 and 99.4% at the 2-year follow-up (p = 0.002), respectively. Male (Hazards ratio [HR] = 3.2) and prior KA for anterior cruciate ligament (ACL) injury (HR = 4.4) were associated with postoperative complications in the KA group. There was a non-linear relationship between time from prior KA to TKA and postoperative complications with the turning point at 9.4 months. Conclusion Prior KA is associated with worse outcomes following subsequent TKA, especially male patients and those with prior KA for ACL injury. There is an increased risk of postoperative complications when TKA is performed within nine months of KA. Surgeons should keep these findings in mind when treating patients who are scheduled to undergo TKA with prior KA.

Abstract Background The optimal time to perform a total knee arthroplasty (TKA) after knee arthroscopy (KA) was controversial in the literature. We aimed to 1) explore the effect of prior KA on the subsequent TKA; 2) identify who were not suitable for TKA in patients with prior KA; and 3) determine the timing of TKA following prior KA. Methods We retrospectively reviewed 87 TKAs with prior KA and 174 controls using propensity score matching in our institution. The minimum followup was 2 years. Postoperative clinical outcomes were compared between groups. Kaplan-Meier curves were created with reoperation as an end point. Multivariate Cox proportional hazards regressions were performed to identify risk factors of severe complications in the KA group. The two-piecewise linear regression analysis was performed to examine the optimal timing of TKA following prior KA. Results The all-cause reoperation, revision and complication rates of KA group were significantly higher than those of control group (p < 0.05). The survivorship of KA group and control group was 92.0% and 99.4% at the 2-year followup (p = 0.002), respectively. Male (Hazards ratio [HR] = 3.2) and prior KA for anterior cruciate ligament (ACL) injury (HR = 4.4) were associated with postoperative complications in the KA group. There was a non-liner relationship between time from prior KA to TKA and postoperative complications with the turning point at 9.4 months. Conclusion Prior KA is associated with worse outcomes following subsequent TKA, especially male patients and those with prior KA for ACL injury. The optimal timing of TKA may be 9 months after prior KA. Surgeons should keep these findings in mind when treating patients who are scheduled to undergo TKA with prior KA.