Considering a BMI Cutoff for Total Knee Arthroplasty Patients
When a patient has a body mass index (BMI) of 40 or above, should the surgeon withhold total knee arthroplasty (TKA) until the patient loses weight to avoid the possible increased risk of complications?
It’s not a bad idea, according to a 2013 statement from a work group of the American Association of Hip & Knee Surgeons. Surgeons should consider delaying the procedure in these patients, the work group said, particularly if the patients have comorbidities that would put them at greater risk for complications, such as poorly controlled diabetes or malnutrition. 
But research shows that only about 20% of patients with a high BMI will be able to lose enough weight to bring their BMI under 40 before surgery – and that they won’t necessarily lose the weight after TKA either. 
With that in mind – and with the growing number obese individuals in the US  – the question becomes this: Should a significant part of the population with disabling osteoarthritis be restricted from undergoing a procedure that could provide pain relief and allow them greater mobility?
The answer, according to Gwo-Chin Lee, MD, and William G. Hamilton, MD, is no: Patients with osteoarthritis of the knee should be treated as individuals, not as a number. Speaking at the 6th Annual ICJR South Hip & Knee Course, both surgeons said they believe this is the best, most compassionate approach to managing patients with a high BMI.
Dr. Lee, from the University of Pennsylvania in Philadelphia, noted that “big data” show an association between high BMI and an increased incidence of complications after TKA. But big data can be misleading, even contradictory, he said, and coding errors or “overcoding” of obesity can lead to false associations. 
It’s important for the surgeon to engage with patients with a high BMI and to help those who can reasonably be helped, Dr. Lee said, including working to modify risk factors that can be modified – and understanding that BMI may not be modifiable. Ultimately, he said, imposing an arbitrary BMI cutoff is not based in the evidence and is bad medicine.
Dr. Hamilton, from Anderson Orthopaedic Research Institute in Alexandria, Virginia, assures his patients with a high BMI that he will perform their TKA, but that they will first need to work together to make sure the patient is as healthy as possible before surgery to optimize the outcome. He does not schedule surgery during that first visit, but instead initiates visits with medical providers who can evaluate and treat the patient for modifiable risk factors. He will also make a 3-month follow-up visit with the patient to assess progress with these efforts.
The bottom line for Dr. Hamilton: The surgeon needs to be part of the solution for patients with osteoarthritis and a high BMI, ensuring that they understand the pros and cons of surgery at their present weight and that they make decisions together about proceeding with TKA.
Click the images below to hear more of what Dr. Lee and Dr. Hamilton had to say about BMI cutoffs.
Gwo-Chin Lee, MD
William G. Hamilton, MD
Dr. Lee and Dr. Hamilton have no disclosures relevant to these presentations.
- Workgroup of the American Association of Hip and Knee Surgeons Evidence Based Committee. Obesity and total joint arthroplasty: a literature based review. J Arthroplasty. 2013 May;28(5):714-21. doi: 10.1016/j.arth.2013.02.011. Epub 2013 Mar 19.
- Ast MP, Abdel MP, Lee YY, Lyman S, Ruel AV, Westrich GH. Weight changes after total hip or knee arthroplasty: prevalence, predictors, and effects on outcomes. J Bone Joint Surg Am. 2015 Jun 3;97(11):911-9. doi: 10.2106/JBJS.N.00232.
- Odum SM, Springer BD, Dennos AC, Fehring TK. National obesity trends in total knee arthroplasty. J Arthroplasty. 2013 Sep;28(8 Suppl):148-51. doi: 10.1016/j.arth.2013.02.036. Epub 2013 Aug 15.
- George J, Newman JM, Ramanathan D, Klika AK, Higuera CA, Barsoum WK. Administrative databases can yield false conclusions-an example of obesity in total joint arthroplasty. J Arthroplasty. 2017 Sep;32(9S):S86-S90. doi: 10.1016/j.arth.2017.01.052. Epub 2017 Feb 7.