Frailty and Sarcopenia as Predictors of Functional Recovery After Total Hip and Knee Arthroplasty: A Narrative Review

Introduction: Total hip arthroplasty (THA) and total knee arthroplasty (TKA) volumes continue to rise, yet postoperative functional recovery and physical therapy (PT) utilization remain highly variable. Frailty and sarcopenia capture biological vulnerability beyond chronological age and may better explain heterogeneity in rehabilitation needs and recovery trajectories. Methods: We conducted a qualitative narrative review guided by SANRA recommendations. PubMed, Scopus, Web of Science, CINAHL, and Google Scholar were searched for English-language studies (January 2000-December 2025) involving adults undergoing THA/TKA that assessed preoperative frailty and/or sarcopenia and reported postoperative functional or rehabilitation-related outcomes. Data were extracted and synthesized thematically without quantitative pooling. Results: Thirty-four studies met inclusion criteria. Despite heterogeneous definitions and measures, both frailty and sarcopenia were consistently associated with slower early mobility, poorer functional recovery, longer hospital stays, and higher rates of non-home discharge. Frailty showed stronger links to post-acute care use and healthcare costs, whereas sarcopenia was more closely tied to impaired early function, delayed ambulation, and greater reliance on assistive devices. Frailty may improve after arthroplasty in some patients, while sarcopenia often represents a more persistent, muscle-specific limitation. Direct reporting of PT dose was uncommon, with only a minority of included studies explicitly reporting physical therapy frequency, duration, or intensity, limiting the ability to assess dose-response relationships. Conclusions: Preoperative frailty and sarcopenia are clinically meaningful predictors of functional recovery and rehabilitation utilization after THA/TKA and support vulnerability-informed discharge planning and stratified rehabilitation pathways. Future prospective studies should standardize vulnerability assessment and directly quantify PT dose, setting, and patient-centered outcomes to inform and test vulnerability-guided rehabilitation strategies, including prehabilitation.