The American College of Rheumatology and American Association of Hip and Knee Surgeons have issued new evidence-based recommendations challenging current surgical practices that delay total knee arthroplasty until patients meet specific body mass index thresholds. The guideline conditionally recommends against delaying surgery solely for the purpose of reaching a target body mass index, while continuing to support postponement in cases of poorly controlled diabetes or active nicotine use.

These conditional recommendations were based on a systematic review of the evidence regarding optimal surgical timing in patients with symptomatic moderate-to-severe osteoarthritis (OA) for whom nonoperative therapy has been ineffective. The guideline emphasizes the importance of individualized, shared decision-making between physician and patient, particularly when the quality of evidence is low or patient preferences and cost considerations are relevant.

“The guideline conditionally recommended against delaying surgery to meet rigid weight or body mass index (BMI) thresholds,” the guideline authors noted, reflecting a departure from common institutional practices requiring weight loss prior to total knee arthroplasty (TKA).

Case Example Highlights Clinical Debate

The implications of the guideline are illustrated by the case of a 70-year-old female patient with bilateral knee OA and a BMI of 51 kg/m². Although considered a candidate for TKA, her surgeon required a BMI below 40 kg/m² before proceeding. The patient had multiple comorbidities—including prediabetes and irritable bowel syndrome (IBS)—and had experienced persistent pain and mobility limitations despite nonoperative treatments.

Two specialists offered differing approaches. Tara Skorupa, MD, of the Beth Israel Deaconess Medical Center, recommended surgery without further delay:

“Given the mixed data for benefit of delaying [total joint arthroplasty] (TJA) for additional weight loss, the potential for further weight gain in delaying surgery, and the significant socioeconomic barriers to the most effective weight loss strategies, I would recommend proceeding to TJA without delay.”

In contrast, Ayesha Abdeen, MD, Chief of Hip and Knee Arthroplasty at Boston Medical Center, emphasized the importance of risk mitigation:

“Given the evidence indicating that obesity is associated with significant medical and surgical risk for patients with a BMI over 40 kg/m², it is reasonable that TJA be initially delayed for patients with a BMI over this threshold.”

Evidence Supporting Risk Stratification

Extensive data confirm increased perioperative risk associated with obesity. Patients with a BMI of 35 to 39.9 kg/m² face a twofold increased risk of deep prosthetic joint infection, whereas those with a BMI ≥ 40 kg/m² experience a fourfold increase. Aseptic loosening is the primary mode of failure in patients with obesity and is associated with higher rates of tibial component failure requiring revision.

Dr. Abdeen explained:

“Obesity is an independent risk factor for medical complications after TJA, including cardiovascular and respiratory events and venous thromboembolism. Many studies found an increased risk for complications, including in-hospital death, at a BMI threshold greater than 40 kg/m².”

Nevertheless, the benefit of preoperative weight loss remains uncertain. A recent trial evaluating weight loss of 5% or more in patients with a BMI greater than 40 kg/m² reported similar complication rates among those who lost weight compared with those whose weight remained stable, but a higher risk among patients who had recently gained weight. Notably, 29.3% of patients who underwent bariatric surgery declined TKA as a result of  symptom improvement.

Emerging Treatment Options for Obesity

The discussion highlighted promising medical weight loss therapies. In a recent randomized controlled trial of semaglutide in patients with obesity and knee OA, those receiving semaglutide experienced significantly greater weight loss (13.7% vs 3.2% with placebo), with corresponding improvements in pain and function. A 5% to 10% weight loss can improve pain with a similar magnitude to oral analgesics (ES, 0.33),” Dr. Skorupa noted.

However, access to glucagon-like peptide (GLP)-1 receptor agonists remains limited. Among individuals without diabetes, out-of-pocket costs may exceed $1,000 per month, and gastrointestinal side effects may limit use, particularly for those with IBS.

Bariatric surgery, while effective in reducing weight and potentially improving symptoms, carries both short- and long-term risks. Although some trials have demonstrated a reduced risk of postoperative complications when bariatric surgery is performed prior to TKA, the benefit appears primarily short-term. The guideline cautions against requiring bariatric surgery solely to qualify for arthroplasty.

Emphasis on Shared Decision-Making

Both experts emphasized the importance of individualized, longitudinal care planning. Dr. Abdeen explained:

“It’s not a simple one-time conversation; it’s a process. So, in the instance of [this female patient], who I am instructing to lose weight, I wouldn’t send her out without any further follow-up. We would give reasonable timeframes to check back in, and to see how she is managing with mitigating her current risk.”

The guideline underscores that conditional recommendations apply when “the evidence quality is low or very low, when the decision is sensitive to individual patient preferences, or when costs are expected to impact the decision.” For the female patient, whose hemoglobin A1c was 6.1% and who didn't use tobacco, obesity remained her primary modifiable risk factor.

Clinical Implications

These new guidelines may affect thousands of surgical decisions annually, as more than 14 million Americans have symptomatic knee OA—a number expected to increase with population aging and rising obesity rates.

The debate reflects broader challenges related to health equity and access. Socioeconomic barriers often hinder effective weight loss, and rigid BMI cutoffs may inadvertently delay beneficial procedures among patients unable to meet them.

The American College of Rheumatology/American Association of Hip and Knee Surgeons guideline represents the first formal, evidence-based recommendation addressing optimal timing of TKA in high-risk populations. While its recommendations are conditional, they reflect a shift away from inflexible surgical eligibility criteria toward more nuanced, patient-centered decision-making.

Source: Annals of Internal Medicine