IntroductionThe safety and benefits of single stage bilateral total knee arthroplasty (SSBTKA) among older patients as compared to unilateral TKA remains controversial. This study aimed to evaluate the influence of age and comorbidities on complications and early outcomes for unilateral and BTKA in patients over and under 70 years of age. Materials and methods This prospective study compared postoperative complications and early patient-reported outcomes at 6 weeks of 142 unilateral TKA patients (N = 75, ≤ 70; N = 67, > 70) and 89 SSBTKA patients (N = 48, ≤ 70; N = 41, > 70). Patients completed the KOOS JR and PROMIS Global Mental (GMH) and Global Physical Health (GPH) surveys. Knee Society Scores for Knee (KSS-K) and Function (KSS-F) were completed in the clinic. Parametric tests were performed for comparisons of unilateral and BTKA outcomes and complications for patients over and under 70. Results While patient demographics were similar, patients > 70 had more comorbidities than patients ≤ 70 (p < 0.004). There were no significant differences in postoperative complications or readmissions between age groups or procedures. Unilateral TKA patients > 70 had significantly lower pre-(p < 0.001) and post-operative (p = 0.011) KSS-F scores compared to those ≤ 70. SSBTKA patients > 70 had significantly higher preoperative GMH (p = 0.029), postoperative KSS-K (p = 0.027), KOOS JR scores (p = 0.039) and satisfaction (p = 0.048) compared to those ≤ 70. Conclusion Age did not influence the risk of early postoperative complications. Additionally, the greater improvements in KOOS JR and higher patient satisfaction for SSBTKA patients > 70 suggests that SSBTKA may meet elderly patient expectations and should not necessarily be discouraged due to safety concerns.

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