Is There a Body Mass Index Threshold for Patients Undergoing Primary Total Knee Replacement—A Literature Review

<b>Background:</b> Osteoarthritis (OA) is a prevalent degenerative joint disease and a major cause of disability in the aging population. Total knee arthroplasty (TKA) is a common intervention for advanced OA, yet postoperative outcomes may vary, particularly among individuals with obesity. Elevated body mass index (BMI) is a recognized risk factor for the development and progression of OA and may influence perioperative and postoperative complication rates. <b>Objective:</b> This literature review evaluates whether a specific BMI threshold should guide eligibility for primary TKA, with particular emphasis on the impact of BMI on surgical risk, implant outcomes, and functional recovery. <b>Methods:</b> A systematic search was conducted across PubMed (MEDLINE), Cochrane Library, EMBASE, and Google Scholar to identify peer-reviewed studies from the past two decades examining the relationship between BMI and clinical outcomes following primary TKA. <b>Findings:</b> Higher BMI-especially ≥40 kg/m²-is consistently associated with increased perioperative and postoperative complications, including wound issues, infection, thromboembolic events, longer hospital stay, and higher revision risk. Despite these elevated risks, evidence demonstrates that obese and morbidly obese patients experience substantial improvements in pain, mobility, and function that are comparable in magnitude to those seen in non-obese individuals. The literature does not support a universally applicable BMI cutoff for determining surgical eligibility. <b>Conclusions:</b> BMI is an important modifier of surgical risk but should not be used as an absolute criterion for excluding patients from TKA. Instead, a personalized approach is recommended-one that considers BMI within the context of comorbidities, functional limitation, patient motivation, and opportunities for preoperative optimization. With appropriate patient selection and risk-mitigation strategies, TKA remains a clinically valuable and justified intervention across all BMI categories.