Biological Age Acceleration Predicts Functional Decline and Surgical Risk in Knee Arthroplasty.

<h4>Background</h4>Chronological age is widely used in perioperative risk assessment, but does not adequately capture interindividual differences in physiological reserve. Recently developed phenotypic biological aging measures quantify biological age using clinical biomarkers and may better reflect frailty and surgical vulnerability. This study compared the predictive value of biological and chronological age for functional and perioperative outcomes in patients undergoing total knee arthroplasty (TKA).<h4>Methods</h4>We retrospectively analyzed 173 consecutive adults who had osteoarthritis undergoing TKA. Biological aging metrics were calculated from nine standard blood biomarkers using a previously validated algorithm. Outcomes included total and limb skeletal muscle mass, 10-meter gait time, and overall and symptomatic perioperative complications. Associations were assessed using multivariable linear and logistic regression models adjusted for sex, body mass index, body weight, frailty status using the 11-item modified frailty index, diabetes mellitus, and hypertension. Predictive performance was evaluated using adjusted R² and area under the curve with 95% confidence intervals (CI).<h4>Results</h4>Biological age acceleration was associated with slower gait time (β = 0.48 seconds/year, P < 0.001; R² = 0.19), outperforming chronological age (R² = 0.05). In adjusted logistic regressions, biological age acceleration was associated with increased odds of overall perioperative complications, including asymptomatic deep vein thrombosis detected by routine ultrasonography (odds ratio = 1.19 per one-year increase, 95% CI 1.11 to 1.27, P < 0.001), with good discrimination (area under the curve = 0.77). This association persisted for symptomatic complications (odds ratio = 1.11, 95% CI: 1.04 to 1.19, P = 0.003). Chronological age was not associated with complications (P = 0.34). Daily alcohol consumption and smoking are modifiable correlates of accelerated biological aging.<h4>Conclusions</h4>Biological aging metrics better reflected perioperative vulnerability than chronological age in patients undergoing TKA and may support individualized risk stratification and lifestyle optimization.