TOPLINE: 

Semaglutide and tirzepatide added to usual care showed potential as cost-effective treatments for patients with knee osteoarthritis and obesity, with tirzepatide offering benefits at lower costs. In patients eligible for bariatric surgery, Roux-en-Y gastric bypass was a cost-effective treatment strategy.

METHODOLOGY:

• Researchers used the Osteoarthritis Policy Model, a validated microsimulation model, to assess the cost-effectiveness of treatments and weight-loss interventions for knee osteoarthritis and obesity.
• The study included patients with knee osteoarthritis and obesity from the phase 3 STEP-9 study (mean age, 56 years; 81.6% women; 88.9% non-Hispanic White), with a mean BMI of 40.3 and a mean pain score of 70.9 on the Western Ontario and McMaster Universities Osteoarthritis Index of 0-100, indicating low to worst pain.
• The interventions under comparison included usual care, usual care with diet and exercise, semaglutide, tirzepatide, laparoscopic sleeve gastrectomy, or Roux-en-Y gastric bypass.
• Primary outcomes measured were quality-adjusted life-years (QALYs) and costs. Cost effectiveness was assessed by comparing incremental cost-effectiveness ratios against $100,000 per QALY, with strategies considered "cost-effective" when their ratios (vs the next least costly alternative) remained below this limit.
• Weight loss for semaglutide and tirzepatide were derived from trials, and annual costs were estimated using net prices of the medication including costs of lifestyle coaching reported by the US Office of Health Policy. Background costs were derived from the Centers for Medicare & Medicaid Services and National Health and Nutrition Examination Survey , considering indirect costs from knee pain.

TAKEAWAY:

• Usual care provided 9.59 QALYs at a lifetime cost of $222,300, diet and exercise yielded 9.75 QALYs for $226,300, and semaglutide offered 10.48 QALYs at $273,500, with tirzepatide providing 10.68 QALYs at a lifetime cost of $280,000.
• Adding tirzepatide to usual care was found to be more cost-effective than adding semaglutide, with an incremental cost-effectiveness ratio of $57,400 per QALY compared with diet and exercise.
• In patients eligible for bariatric surgery (BMI ≥ 35), Roux-en-Y gastric bypass offered greater health benefits and cost savings and had an incremental cost-effectiveness ratio of $30,700 per QALY, compared with laparoscopic sleeve gastrectomy, and dominated semaglutide and tirzepatide.
• Tirzepatide had a 64% probability of being cost-effective at a threshold of $100,000 per QALY, compared with 34% for semaglutide. Roux-en-Y gastric bypass was cost-effective in 68% of scenarios at this threshold, and laparoscopic sleeve gastrectomy in 17%.

IN PRACTICE:

"This direct comparison between prescription medication and bariatric surgery may assist policymakers in setting policy recommendations related to treatment options for persons with knee osteoarthritis and obesity who would be eligible for both surgical and nonsurgical interventions. Clinicians may consider discussing the differences between these weight loss interventions, their potential benefits and harms, and currently available knee osteoarthritis care options with their eligible patients," the authors of the study wrote.

SOURCE:

The study was led by Daniel J. Betensky, Brigham and Women's Hospital in Boston. It was published online on September 15, 2025, in Annals of Internal Medicine.

LIMITATIONS: 

Data on GLP-1 receptor agonists' long-term efficacy and adherence were limited. The exclusion of muscle mass loss as an adverse event could overlook potential physical frailty. The societal perspective did not account for productivity losses from bariatric surgery. Current data may not capture future developments in weight-maintenance effectiveness or adverse events.

DISCLOSURES:

The study was supported by grants from the Arthritis Foundation and the National Institute of Arthritis and Musculoskeletal and Skin Diseases. Some authors reported being consultants and receiving research grants/contracts from various sources. 

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.