Clinical and functional outcomes of primary total knee arthroplasty in patients aged ≥ 80 years compared with younger patients: a systematic review and meta-analysis

Advanced age is closely associated with perioperative and postoperative outcomes following total knee arthroplasty(TKA). Nevertheless, the clinical safety profile and functional recovery of primary TKA in patients aged ≥ 80 years remain incompletely defined. We carried out this systematic review and meta‑analysis synthesizing existing evidence to compare safety as well as clinical effectiveness following TKA between patients aged ≥ 80 years individuals and patients aged below 80 years. Retrieval of pertinent studies from PubMed, Web of Science, Embase, and the Cochrane Library was finished with January 15, 2026 serving as the final cutoff date. Studies satisfying predefined eligibility criteria were enrolled to compare clinical outcomes following TKA between patients aged ≥ 80 years and younger patients. The evaluated endpoints encompassed post-operative complications, mortality, patient-reported outcome measures (PROMs), transfusion requirements, and hospital length of stay. All quantitative syntheses were performed adopting random-effects models.The GRADE approach was used to assess certainty of evidence. Data from 20 observational studies including 447,336 patients were included in the final analysis. The pooled data revealed that patients aged ≥ 80 years had longer hospital stays (MD: 1.28 days; 95% confidence interval [CI]: 0.57 to 1.98; P = 0.0004), higher mortality (RR 3.18; 95% CI: 1.94 to 5.20; P < 0.00001), higher transfusion rate(RR 2.19; 95% CI: 1.63 to 2.95; P < 0.00001), and higher cardiac complications rate(RR 2.20; 95% CI: 1.88 to 2.56; P < 0.00001).Compared to younger patients TKA recipients, the infection rate (RR 1.17; 95% CI: 0.91 to 1.51; P = 0.21) ,thrombosis rate (RR 1.15; 95% CI: 0.97 to 1.36; P = 0.11) and knee society scores (MD:-0.64; 95% CI: -1.95 to 0.67; P = 0.34) were similar across both cohorts. In this meta-analysis of retrospective observational studies, patients aged ≥ 80 years had higher systemic complications and mortality than younger patients. However, functional improvement may be comparable in selected patients. These findings are associations and are limited by confounding, selection bias, and heterogeneous follow-up. Chronological age alone should not preclude TKA. Future prospective and registry-based studies with standardized outcomes and risk adjustment are needed to identify which patients aged ≥ 80 years benefit most. III Systematic Review and MetaAnalysis.GRADE certainty of evidence low to very low.