Sarcopenia and Postoperative Outcomes Following Total Knee Arthroplasty: A Systematic Review of Observational Studies

Purpose: Sarcopenia has emerged as a potential prognostic factor for postoperative complications, functional recovery, patient-reported outcomes, and healthcare costs in patients undergoing total knee arthroplasty (TKA). This systematic review aimed to evaluate its impact on these outcomes following primary TKA. Methods: A systematic review was conducted according to PRISMA guidelines and prospectively registered in PROSPERO (CRD420261320013). PubMed/MEDLINE, EMBASE, and Cochrane Library were searched up to 1 December 2025. Comparative clinical studies including sarcopenic and non-sarcopenic patients undergoing primary TKA and reporting postoperative outcomes were included. Methodological quality was assessed using the MINORS tool. Due to heterogeneity in study design, diagnostic criteria, and outcome measures, a narrative synthesis was performed. Results: Nine studies including more than 93,000 patients were analyzed. Sarcopenia prevalence ranged from 7.7% to 25%. Sarcopenic patients demonstrated higher rates of postoperative complications, including medical events, blood transfusion, falls, fractures, reoperations, and implant-related complications. Functional recovery was delayed, particularly in patients with sarcopenic obesity, with slower improvements in range of motion and gait speed. Although both groups improved after TKA, short- to mid-term patient-reported outcomes were often inferior in sarcopenic patients, while long-term differences were less consistent. Sarcopenia was also associated with longer hospital stay and increased healthcare costs. Conclusions: Sarcopenia is associated with worse postoperative outcomes following primary TKA and may represent a modifiable risk factor for perioperative optimization.