Objective <p>This study aimed to evaluate the prevalence and risk factors of sarcopenia in patients with knee osteoarthritis (KOA) through a systematic review and meta-analysis.</p> Methods <p>A comprehensive search was conducted in PubMed, Web of Science, Cochrane Library, Scopus, China National Knowledge Infrastructure, and WanFang databases for studies published between January 2000 and June 2025. Eligible studies were screened according to predefined inclusion and exclusion criteria. Data were extracted, study quality was assessed, and meta-analyses were performed using Stata 17.0.</p> Results <p>A total of 35 studies involving 13,528 KOA patients were included, of whom 3597 were diagnosed with sarcopenia. The pooled prevalence of sarcopenia and sarcopenic obesity was 25.07% (95% CI 18.85–31.29%) and 12.06% (95% CI 8.24–15.87%), respectively. Subgroup analyses revealed that sarcopenia prevalence increased with disease severity, reaching 26.01% (95% CI 16.27–35.75%) in patients with Kellgren–Lawrence grade 4 KOA. Prevalence was 25.65% (95% CI 20.30–31.00%) among female and 25.85% (95% CI 18.64–33.06%) among Asian populations. Among patients with osteoporosis and diabetes mellitus, prevalence rates were 21.68% (95% CI 8.84–34.53%) and 28.36% (95% CI 17.43–39.29%), respectively. Additionally, sarcopenia was more common among alcohol consumers (30.72%, 95% CI 15.58–45.86%) and smokers (29.82%, 95% CI 18.87–40.77%), with the prevalence being notably higher at 35.20% (95% CI 28.09–42.31%) among patients with irregular physical activity.</p> Conclusion <p>Sarcopenia and sarcopenic obesity are highly prevalent in patients with KOA and are significantly associated with disease severity, gender, geographic region, comorbidities, and lifestyle factors. These findings highlight the clinical importance of assessing sarcopenia in KOA management. Early screening and timely interventions may improve patient outcomes and quality of life.</p>