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BMI Cutoffs are Bad Medicine – High BMI¹ Individuals Deserve Access to Total Knee Replacement Surgery

By Lindo Bacon, PhD

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Denied surgery due to high BMI? Here’s what you and your doctor need to know.  This paper reviews the research on Total Knee Replacement Surgery and provides cultural critique. It’s conclusions are applicable along the spectrum of denied surgeries.

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Comments from an advance reader

My father and I visited orthopedic surgeons with the same knee complaint. My doctor prescribed physical therapy and, when that wasn’t sufficient, surgery. Now, years post surgery, I enjoy full pain-free mobility and have returned to being physically active.

My father’s doctor, on the other hand, prescribed exercise and a calorie restriction diet. The result? Disordered eating. A view of exercise as punishment for weighing too much. Shame. My father died with debilitating knee pain, limited ability to be physically active, and a host of other disorders that can be improved through better fitness.

What was the difference between us that resulted in this very different treatment? About 25 BMI points.

“Come back when you’ve lost 50 pounds.” That’s what an orthopedic surgeon told my friend, a former college athlete now in her late 50s, whose osteoarthritic knee pain had become intolerable.

Osteoarthritis is a progressive disease; early conservative treatment typically prevents or slows progression. My friend, however, had been avoiding the doctor, so traumatized by past visits to health care providers. When she finally did see an orthopedic surgeon, she was told that her pain and disability could be resolved through surgery, but that she would need to lose weight before anyone at their facility would conduct the procedure. When she wasn’t amenable to the bariatric surgery he recommended, he suggested diet and exercise.

Most people with high BMIs have favorable outcomes from knee replacement surgery, yet most, like my father and friend, are not afforded the surgery which can help them. My friend’s story has a happier ending, as you’ll see.

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Discrimination is not effective healthcare.

Background

From breast reductions and fertility treatments to gender affirmation surgeries, hip replacements to knee replacements, individuals with high BMIs are often denied access. However, data consistently show that high BMI patients benefit from these potentially life-saving and life-enhancing surgeries, and that arguments to deny eligibility are based on flawed science.

This manuscript evaluates the practice of using BMI cutoffs (denying eligibility beyond a certain BMI) for total knee arthroscopy (TKA). The conclusions are generalizable and apply across the spectrum of denied procedures.

Osteoarthritis (OA) is likely the leading cause of disability in adults, with the knee being the most frequently affected joint². OA is characterized by joint pain and dysfunction caused by joint degeneration³. The prevalence of OA is higher for people with high BMIs⁴. TKA is one of the most successful of all medical procedures⁵, enabling individuals with advanced OA to reduce their pain, increase their function and live more active lives. 

Literature Review

Given space constraints, the research discussed below is non-exhaustive. Systematic literature reviews and meta-analyses are prioritized, when available.

Weight Loss Recommendations

Requiring weight loss – or at least an attempt at weight loss – prior to making TKA available is commonplace⁶. The theory is that restricting elective total joint surgery for those who have a high BMI might incentivize weight loss, which in turn would provide for better outcomes. However, the data show otherwise. My friend, for example, tried diet and exercise and only managed to lose 10 pounds, not enough for her to meet the eligibility criterion set by her surgeon. His advice wasn’t benign, triggering disordered eating, eventual weight regain, and further entrenching feelings of inadequacy and self-blame.

This outcome is entirely predictable from the research literature on prescribing pre-surgical weight loss, and from weight-focused health care in general⁷. Most TKA studies show only a small percentage of patients – about 14% – were able to accomplish weight loss in the year or two before surgery, suggesting that withholding TKA does not effectively incentivize weight loss. Several studies also determined that most people who lose weight prior to TKA regain that weight after surgery⁸.  One study demonstrated that many people who lose substantial weight before TKA gain back that weight and more after the surgery⁹. 

Two systematic reviews of studies which examined the value of weight loss prior to TKA found insufficient evidence to support a benefit^{10 11} . Further, those who lost weight had identical outcomes with those who did not lose weight. Another study found that those who lost weight before TKA had greater likelihood of re-admission compared with the reference group, raising questions about the safety of losing weight prior to undergoing TKA¹². 

Diet and exercise interventions have not been proven to improve TKA outcomes. A large literature review found the quality of evidence of benefit of combining exercise and dietary interventions in older overweight/obese adults with knee OA to be unclear¹³. One study noted that undergoing joint surgery while malnourished from taking in too few calories and breaking down body tissue (dieting!) predicted serious complications involving hematoma formation, infection, and renal and cardiac complications¹⁴. Yet another study determined that malnutrition is an independent risk factor for complications in joint arthroscopy though “morbid obesity” was not independently associated with a significant increase¹⁵. 

The few weight loss interventions used in claims that it is beneficial after TKA have flaws suggesting unreliable conclusions. For example, in reporting on the IDEA (Innovative approaches to Diet, Exercise, and Activity) randomized controlled study, the study most commonly presented to suggest weight loss interventions before TKA have favorable results, the last data point was obtained at the conclusion of the intervention¹⁶. This is a deceptive snapshot; other research demonstrates that favorable outcomes post TKA for high BMI individuals manifest in the long-term, not the short term¹⁷, and that in general, people rarely maintain lost weight, with one third to two thirds regaining more weight than they lost¹⁸.

Many high BMI individuals are advised to have bariatric surgery before having access to TKA¹⁹. Yet, with bariatric surgery too, there is no evidence of reduced complications or improved outcomes. For example, one systematic review found bariatric surgery prior to TKA does not significantly reduce complication rates or improve clinical outcomes between those who had bariatric surgery prior to joint surgery and those who did not²⁰. A second review determined that the literature remains conflicted on the impact of bariatric surgery prior to total joint arthroscopy (TJA) on complications and the effect on outcomes has yet to be elucidated²¹. In one study including nearly 40,000 Medicare patients, having bariatric surgery before joint surgery increased the likelihood of complications, predicting hematoma formation, infection, and renal and cardiac complications²² when compared to both “obese” and “non-obese” patients, while another study found increased risk for revisions²³. 

Furthermore, delaying treatment pending weight loss gives OA, a progressive disease²⁴, opportunity to worsen, potentially making the procedure more difficult and increasing vulnerability to perioperative complications and poor outcome.

In sum, recommendations to lose weight prior to TKA not only fail to produce the desired results, but may be causing harm. Few people accomplish the recommended weight loss prior to TKA; there isn’t evidence that weight loss, when it does occur, is beneficial; and many people regain the weight after surgery, with some gaining even more. Additionally, pre-TKA diet and exercise programs and bariatric surgery haven’t proven to be beneficial, with some studies indicating harm. These results mirror what has been found when recommending weight loss in general²⁵. As a result, there is a growing movement that suggests that recommendations to lose weight are not only ineffective and harmful, but also unethical²⁶.

My friend tried to lose weight in the 6 month interval between appointments. Demoralized and ashamed that she only lost 10 pounds, insufficient for the surgeon, my friend resigned herself to becoming dependent on using a wheelchair. I asked her if I could support her in seeing her doctor again and act as her advocate. She agreed.

Though slender myself, weight studies are my field of expertise and I am quite familiar with stories of medical fatphobia. But even I was floored watching my friend’s exchange with the surgeon at that appointment. There was the doctor, acting like a benevolent father who just wanted to support her in good health. He was disappointed that she was “non-compliant.” The 250 minutes of exercise she got a week on the stationary bike wasn’t enough to satisfy him, nor did he approve of the appetite control app she was using and the diet she had tried, and instead tried to impose the Mediterranean diet onto her. (Like most doctors, he has no training in weight loss and was simply expounding conventional “wisdom.”) And there was my friend, who I know to be an extremely intelligent, confident, and articulate woman, ashamed and acting like a meek child cowering in front of daddy. Even her voice changed. It was heartbreaking to witness.

The doctor justified denial of surgery by suggesting that her BMI placed her at high risk for infections and poor outcome. Neither of these is supported by the data, as will be discussed soon. 

Industry Protocol

My friend’s doctor was following protocol common in the field. The American Association of Orthopedic Surgeons (AAOS) suggests weight loss be recommended to patients with symptomatic OA of the knee and a Body Mass Index (BMI) ≥ 25 kg/m², which is the lower cutoff defining “overweight,” prior to TKA²⁷, with no explicit mention of protocol if the patient is unable (or unwilling) to lose the weight. For those with a BMI>40, they recommend delaying surgery pending successful weight loss²⁸. Many insurance companies, like my friend’s, allow individual surgeons to independently decide whether to use a BMI cutoff²⁹.

Surgical Complications and Outcomes

Data examining how high BMI individuals seeking TKA fare in OA-related pain or function if they undertake TKA versus not have not been obtained. The studies with intriguing titles like “Fate of the morbidly obese patient who is denied total joint arthroplasty” only address weight loss^{30 31}.

Instead, the research cited to evaluate the value of BMI cutoffs typically compares the TKA outcomes of high BMI individuals to “normal” BMI individuals. This is problematic: Whether thinner people have better health outcomes is irrelevant to the question of whether to provide medical care to higher BMI people. Further, individuals with “normal” BMIs, like people with privilege of any kind, are likely to have better health outcomes³² than people who are disadvantaged by weight bias and also likely to have other marginalized identities and characteristics that put them at greater health risk³³. 

Nonetheless, for the purpose of discussion, these studies are reviewed. Of the six systematic reviews of investigations comparing outcomes of high BMI individuals to “normal weight” individuals following TKA, none suggested a BMI cutoff is warranted³⁴ . Four of the six reviews determined that despite having poorer outcomes than lower BMI individuals, the worser outcomes are not substantial enough to warrant withholding TKA^{35 36 37 38}. The fifth review determined that a statistically significant difference in overall complication rate between individuals with a BMI>40 and the “normal” BMI reference group was only found in three of eight studies³⁹. The remaining review, the largest, includes 37 studies and determined that functional outcome improvements in “obese” individuals are similar to those in “non-obese” individuals⁴⁰.

In one of those reviews, the authors noted that the degree of change in functional outcome within BMI groups following TKA is a more important metric than comparison of outcome between BMI groups, though the latter is more commonly considered⁴¹. Their retrospective review determined that while individuals with higher BMIs had worse preoperative and post operative functional scores, their benefit from surgery measured by the change in functional scores showed no difference compared to patients with lower BMI. 

The UK maintains a large National Joint Registry which also supports these conclusions⁴². Investigators analyzed 493,710 TKAs and determined that there is “no evidence of poorer outcomes in patients with high BMI.” Their paper explicitly states rationing TKA based on high BMI is unwarranted.

There is no accepted metric that establishes how much or what kind of a differential between complication rates or outcomes makes denying access to care acceptable. Putting the risk in perspective, one study reviewed over 27,000 total joint arthroplasties. They determined that despite a small increase in complications for individuals with a BMI>40, these patients still benefit from total joint arthroplasty and concluded that instituting “a 30 kg/m2 criterion for total joint arthroplasty eligibility is marginally better than flipping a coin and should not determine surgical eligibility⁴³.” They also found that if patients with BMI ≥40 had not been permitted to undergo surgery, 14 would have been denied complication-free surgery for every 1 who would have been spared a complication.

While the short-term surgical results have been well-researched, longer term outcomes are less studied. When longer term studies are conducted, at two years⁴⁴, and five years⁴⁵, high BMI individuals have similar (excellent) outcomes to others, including substantial functional gain and pain relief. A nine-year study determined that while a BM≥35 has “a small but significant adverse effect on clinical outcome,” there was no difference in the overall complication rates or implant survival between the “obese” and “non-obese” groups, and “significant improvements in outcome are sustained in all groups [BMI<30, BMI=30-35 and BMI≥35]⁴⁶.” Their conclusion: “Given the substantial, sustainable relief of symptoms after TKR [Total Knee Replacement] and the low peri-operative complication and revision rates in these two groups [BMI=30-35 and BMI≥35], we have found no reason to limit access to TKR in obese patients.” 

In fact, there is substantial emerging evidence demonstrating that “obese” individuals undergoing TKA have lower mortality risk compared with lower BMI individuals⁴⁷. A finding that suggests high weight may be protective is not unusual. A meta-analysis of 2.88 million participants conducted by the U.S. Centers for Disease Control (CDC) found the hazard ratios for all-cause mortality were in fact lowest in “overweight” individuals and that individuals with BMIs categorized as “grade I obesity” (i.e., 30-35) actually had the same risk as individuals with a “normal” BMI (18.5-25)⁴⁸.

Indeed, hundreds of investigations have shown many conditions where high BMI individuals have a more favorable mortality prognosis than low BMI individuals, including coronary heart disease, hypertension, heart failure, stroke, type 2 diabetes, chronic obstructive pulmonary disease, and osteoporosis⁴⁹. Ironically, higher survival rates have also been found following surgery (non-bariatric) and acute hospitalization for infection (one of the complications suggested to be increased in higher weight individuals following TKA)⁵⁰.

Perhaps weight itself may play little or no role in the associations and underlying confounding factors better explain outcomes⁵¹. For example, low albumin levels often co-occur with “obesity.” One investigation sought to understand whether low albumin levels may be a confounder that mediates the relationship between BMI and outcome of TKA⁵². They analyzed records of 77,785 patients in The National Surgical Quality Improvement Program database and determined that low serum albumin, but not morbid obesity, was independently associated with a greater risk of perioperative complications. This is an important finding as low serum albumin may be more modifiable than high BMI.

Fitness, also more modifiable than BMI, is another confounder⁵³. Higher levels of fitness are associated with prolonged life expectancy across all levels of adiposity⁵⁴. Also, it has been observed that high fitness attenuates or eliminates the health risk associated with high BMI⁵⁵ and that fitness is more highly associated than fatness for mortality in general and cardiovascular-related mortality specifically⁵⁶. Indeed, data illustrate that low cardiorespiratory fitness is more hazardous than is high BMI⁵⁷. Increases in physical activity are consistently associated with greater reductions in mortality risk than intentional weight loss. Further, most cardiometabolic risk markers associated with obesity can be improved with exercise training independent of weight loss⁵⁸. It is ironic that health concern is expressed for high BMI individuals while they are denied the very procedure that may best allow them to improve their fitness and overall health⁵⁹.

Additionally, the increased risk of complications, in the studies in which it has been observed, may in part be iatrogenic (caused by medical treatment). Extensive research establishes that many healthcare providers hold stigmatizing attitudes towards high BMI individuals⁶⁰. Not surprisingly, high BMI individuals have higher rates of perceived weight stigma⁶¹. Perceived weight stigma is associated with functional disability, independent of BMI, as determined in one study of national survey data with a 10-year follow-up⁶². Further, findings show that those who were BMI 30–34.9 and perceived weight discrimination faced greater increases in functional disability than those who were BMI>35 and did not perceive discrimination.

The strong negative attitudes and stereotypes about high weight individuals held by healthcare providers influence perceptions, judgment, interpersonal behavior and decision-making, which results in providing lower quality care⁶³. The probability of a high BMI patient not having experienced fat-shaming by the medical community is extremely low. What’s more likely is that they’ve been given harmful medical interventions in the name of weight loss, while not receiving adequate medical care for actual health conditions. As a result of experiences of or expectations for poor treatment, they often avoid or delay medical care⁶⁴, which in turn may result in missed opportunity to be counseled in more conservative measures that might reduce the progression of OA and the need for TKA. 

Also, most knee replacement implants aren’t designed for high weight bodies – which is ironic as TKA procedures are more commonly performed on high weight individuals⁶⁵ – and a high proportion (16%) of “obese” individuals are receiving knee replacement implants against manufacturer recommendations⁶⁶. Of the 25 knee and hip components reviewed in one study, 5 recommended against implant use in “obese” patients. By using the word ‘caution’ or ‘warning’, 15 of the remaining 20 implants imply there is risk associated with use in high BMI individuals. Only 5 of the 25 implants reviewed did not warn against use in “obese” patients.

Other equipment may also be inadequate. It’s common for example, for blood pressure cuffs to be too small and give inaccurate readings. Gowns and chairs that are too small convey the idea that that larger people don’t matter, adding stress and exacerbating distrust, which are also known to worsen outcomes.

Additionally, inadequate skills of the anesthesia team may also contribute to increased risk for complications⁶⁷. Anesthesia techniques that may work well for a low BMI patient may be inappropriate and unsafe for a high BMI patient⁶⁸. Health providers are often inadequately trained or inexperienced at finding veins, inserting breathing tubes, or determining appropriate dosing for high BMI patients.

The recommendation to lose weight is yet another iatrogenic component. As discussed previously, weight loss has not been shown to reduce risk for complications and may even worsen risk. 

Recognizing the iatrogenic component is critical. This understanding situates the problem in the medical system, as opposed to people’s bodies, helping us redirect our attention to systemic change, which may be more modifiable than a person’s BMI. Applying the right measures and precautions⁶⁹ can lead to good outcomes⁷⁰.

Weight bias shows up in other ways too. For example, the odds of having a complication from TKA for patients with BMI >40 is lower than the odds of a complication for patients with these risk factors: elevated bilirubin, dialysis, history of stroke, hypertension, older than 75 years of age, congestive heart failure, chronic obstructive pulmonary disease, low albumin, ASA > 2, and diabetes⁷¹. Yet, none of those independently render a person ineligible for surgery, which suggests discrimination. 

We can’t know if confounding is present unless we measure confounders. That doesn’t often happen. If we don’t measure weight stigma, we’ll never know about its possible role in anything associated with fat. As there is compelling evidence that weight stigma causes much of the disease we blame on fat, this huge oversight means that our prescriptions are causing the very problem they aim to solve⁷².

Because high BMI is more common among marginalized groups⁷³, instituting a BMI cutoff will result in reduced access to care for people in certain marginalized groups, and worsens racial, gender, and socioeconomic disparities. One recent study pooled data from 21,294 individuals in the 1999–2014 National Health and Nutrition Examination Survey, a highly respected nationally representative US database, and demonstrated that using BMI cutoffs as a criterion for arthroplasty would result in reduced access to care for non-Hispanic blacks compared with non-Hispanic whites, for women compared to men, for people of lower socioeconomic class, and for those with lesser formal education⁷⁴. 

In England, restricting treatment based on BMI is considered unacceptable by the National Institute for Health and Care Excellence (NICE), which is the governmental agency responsible for producing evidence-based clinical guidelines, and the Royal College of Surgeons (RCS) and British Orthopaedic Association (BOA), the most respected professional organizations in their disciplines⁷⁵. Despite this, in 2015, 51% of health facilities had either mandatory weight thresholds or a policy to instruct clinicians to encourage patients to lose weight prior to eligibility. This is up from 44% the previous year⁷⁶. The RCS attribute the failure to follow policy guidelines to weight bias and economics, noting that people feel permission to discriminate against high BMI patients and they “were becoming soft targets for National Health Service (NHS) savings.”

Like Britain, in the United States there is also financial incentive to the health care industry to deny care, mediated by the weight bias discussed previously. Not only does denying care save insurance companies money⁷⁸, but it also shields surgeons from performing surgeries that may take more time, skill, have higher risks⁷⁹ and lower their performance metrics. Surgeons are under increasing pressure from payors, health care systems, and peers alike to have excellent outcomes and to minimize costs. While I don’t condone making medical decisions based on cost, it may put some at ease to know that many studies have established that from a cost-effectiveness perspective, TKA offers good value in patients with a BMI of 40 or greater, including those with multiple comorbidities.

What Clinicians Can Do

Applying the right measures and precautions⁸⁰ can lead to good outcomes⁸¹. Instead of excluding patients based on BMI or recommending weight loss:

1. Health care providers can get educated about weight stigma, recognize how it plays into their interactions with others, and learn techniques to minimize it and provide higher quality care.
2. As with any procedure, patients should be provided with informed consent so they can make an educated choice about whether the surgery is appropriate for them.
3. Office equipment, surgical tools and operative techniques that accommodate bodies of all sizes can be obtained or developed.
4. Surgeons can be judged on their effectiveness at supporting patients’ well-being rather than operating time or complication rates.

Conclusion

What happened to my friend, you may be wondering? I’m not sure which was more persuasive: the data I presented or the threat of lawsuit, but we convinced the surgeon to conduct the procedure. She had the surgery, and, as the data predicted, is doing great, now one year out.

The benefits of total knee replacement surgery are not limited to those who are lean. Delaying surgery pending weight loss is a cause for concern as it is contraindicated by the clinical evidence, ineffective, discriminatory, harms patients, and prolongs pain and immobility that surgery would alleviate. The recommendation to lose weight is also harmful, often backfiring and always increasing stigma and distress, which in turn lead to a long list of diseases, ironically including many of the diseases that get blamed on high BMI.

Review of the literature clearly demonstrates that applying BMI cutoffs for TKA supports the health care industry, at the detriment of the health and well-being of high BMI individuals. Implementing cutoffs results in high BMI individuals becoming increasingly disabled, increasingly unfit, and increasingly immobile because they cannot access a procedure which could help them regain their mobility, decrease their pain, and improve their fitness, supporting health and well-being well beyond their knees. Denying care also worsens weight, racial, gender-based, and socioeconomic disparities.

The problem is not in people’s bodies – it’s in a system that (unwittingly perhaps) takes advantage of fatphobia to save money. Treatment decisions should be based on clinical evidence, not bias or financial considerations. Improved health outcomes for high BMI individuals will be better achieved by a focus on reducing medical weight bias and challenging capitalism’s role in the health industrial complex, rather than restricting care. Even if one is skeptical of this review, I urge all concerned, in the name of compassion, to stop the weight focus. High BMI individuals deserve to live without stigma and discrimination and to have equitable access to surgery.

Acknowledgements

Thanks to Rachel Cook and Shannon Patterson for critical review.

References

Links to the entire article are provided when known to be open access.

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1. Throughout this manuscript, the words “overweight,” “obese,” and “normal” are used when introduced by others. They are placed in quotation marks so as not to contribute to pathologizing and stigmatizing body size. The terms “higher BMI, high BMI, lower BMI, and low BMI” are used at other times in line with recommendations from advocates for reducing weight stigma. When the terms “lower BMI” or “low BMI” are used, they exclude individuals in the “underweight” category. Using a relative term without an explicit anchor point may seem problematic, but is chosen as a compromise forced by the inadequacy of language.
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21.  Gu A, Cohen JS, Malahias MA, Lee D, Sculco PK, McLawhorn AS. The Effect of Bariatric Surgery Prior to Lower-Extremity Total Joint Arthroplasty: A Systematic Review. HSS J. 2019 Jul;15(2):190-200. doi: 10.1007/s11420-019-09674-2. Epub 2019 Apr 9. PMID: 31327952; PMCID: PMC6609675. https://pubmed.ncbi.nlm.nih.gov/31327952/. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6609675/. 
22.  Nickel BT, Klement MR, Penrose CT, Green CL, Seyler TM, Bolognesi MP. Lingering Risk: Bariatric Surgery Before Total Knee Arthroplasty. J Arthroplasty. 2016 Sep;31(9 Suppl):207-11. doi: 10.1016/j.arth.2016.02.075. Epub 2016 Mar 15. PMID: 27179771. https://www.arthroplastyjournal.org/article/S0883-5403(16)00270-9/fulltext
23.  Lee GC, Ong K, Baykal D, Lau E, Malkani AL. Does Prior Bariatric Surgery Affect Implant Survivorship and Complications Following Primary Total Hip Arthroplasty/Total Knee Arthroplasty? J Arthroplasty. 2018 Jul;33(7):2070-2074.e1. doi: 10.1016/j.arth.2018.01.064. Epub 2018 Feb 8. PMID: 29606290. https://pubmed.ncbi.nlm.nih.gov/29606290/.
24.  Castañeda S, Roman-Blas JA, Largo R, Herrero-Beaumont G. Osteoarthritis: a progressive disease with changing phenotypes. Rheumatology (Oxford). 2014 Jan;53(1):1-3. doi: 10.1093/rheumatology/ket247. Epub 2013 Jul 22. PMID: 23878311. https://pubmed.ncbi.nlm.nih.gov/23878311/ https://academic.oup.com/rheumatology/article/53/1/1/1780580
25.  Jeffrey M. Hunger,Joslyn P. Smith,A. Janet Tomiyama. An Evidence-Based Rationale for Adopting Weight-Inclusive Health Policy. First published: 16 January 2020. https://doi.org/10.1111/sipr.12062. https://jeffreyhunger.com/uploads/3/4/4/8/34481134/hunger_smith___tomiyama__2020__-_sipr.pdf. (Verify this is relevant.)
26.  Tracy L. Tylka, Rachel A. Annunziato, Deb Burgard, Sigrún Daníelsdóttir, Ellen Shuman, Chad Davis, Rachel M. Calogero, “The Weight-Inclusive versus Weight-Normative Approach to Health: Evaluating the Evidence for Prioritizing Well-Being over Weight Loss”, Journal of Obesity, vol. 2014, Article ID 983495, 18 pages, 2014. https://www.hindawi.com/journals/jobe/2014/983495/
27. American Academy of Orthopaedic Surgeons. Treatment of Osteoarthritis of the Knee – 2nd Edition Evidence-Based Clinical Practice Guideline. https://www.aaos.org/globalassets/quality-and-practiceresources/osteoarthritis-of-the-knee/osteoarthritis-of-the-knee-2nd-editiion-clinical-practice-guideline.pdf. Published May 18, 2013. 
28. From: https://orthoinfo.aaos.org/en/treatment/weight-loss-and-joint-replacement-surgery/ . Accessed 9/26/2021. [I couldn’t find it in an official document.]
29. Kaiser Permanente is an example. Personal communication, Kenneth Trauner, MD, Kaiser Permanente Oakland, 9/19/21.
30. Springer BD, Roberts KM, Bossi KL, Odum SM, Voellinger DC. What are the implications of withholding total joint arthroplasty in the morbidly obese? A prospective, observational study. Bone Joint J. 2019 Jul;101-B(7_Supple_C):28-32. doi: 10.1302/0301-620X.101B7.BJJ-2018-1465.R1. PMID: 31256642. https://pubmed.ncbi.nlm.nih.gov/31256642/
31. Shapiro JA, Narayanan AS, Taylor PR, Olcott CW, Del Gaizo DJ. Fate of the Morbidly Obese Patient Who Is Denied Total Joint Arthroplasty. J Arthroplasty. 2020 Jun;35(6S):S124-S128. doi: 10.1016/j.arth.2020.01.071. Epub 2020 Feb 4. PMID: 32088050. https://pubmed.ncbi.nlm.nih.gov/32088050/. 
32. Thoits PA. Stress, coping, and social support processes: where are we? What next? J Health Soc Behav. 1995;Spec No:53-79. PMID: 7560850. https://pubmed.ncbi.nlm.nih.gov/7560850/. 
33.  Thornton PL, Kumanyika SK, Gregg EW, Araneta MR, Baskin ML, Chin MH, Crespo CJ, de Groot M, Garcia DO, Haire-Joshu D, Heisler M, Hill-Briggs F, Ladapo JA, Lindberg NM, Manson SM, Marrero DG, Peek ME, Shields AE, Tate DF, Mangione CM. New research directions on disparities in obesity and type 2 diabetes. Ann N Y Acad Sci. 2020 Feb;1461(1):5-24. doi: 10.1111/nyas.14270. Epub 2019 Dec 3. PMID: 31793006; PMCID: PMC7159314. https://pubmed.ncbi.nlm.nih.gov/31793006/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7159314/
34. Ploeger MM, Müller NH, Wirtz DC, Kohlhof H. Adipositas in der Revisionsendoprothetik des Kniegelenks – eine systematische Literaturübersicht und rechtliche Bewertung [Obesity in Revision Total Knee Arthroplasty – a Systematic Review and Legal Assessment]. Z Orthop Unfall. 2018 Aug;156(4):436-442. German. doi: 10.1055/a-0590-5340. Epub 2018 Apr 18. PMID: 29669384. https://www.thieme-connect.com/products/ejournals/abstract/10.1055/a-0590-5340
    Kerkhoffs GM, Servien E, Dunn W, Dahm D, Bramer JA, Haverkamp D. The influence of obesity on the complication rate and outcome of total knee arthroplasty: a meta-analysis and systematic literature review. J Bone Joint Surg Am. 2012;94(20):1839-1844. doi:10.2106/JBJS.K.00820. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3489068/ 
    Boyce L, Prasad A, Barrett M, Dawson-Bowling S, Millington S, Hanna SA, Achan P. The outcomes of total knee arthroplasty in morbidly obese patients: a systematic review of the literature. Arch Orthop Trauma Surg. 2019 Apr;139(4):553-560. doi: 10.1007/s00402-019-03127-5. Epub 2019 Feb 16. PMID: 30778723; PMCID: PMC6420900. https://pubmed.ncbi.nlm.nih.gov/30778723/
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    Chaudhry H, Ponnusamy K, Somerville L, McCalden RW, Marsh J, Vasarhelyi EM. Revision Rates and Functional Outcomes Among Severely, Morbidly, and Super-Obese Patients Following Primary Total Knee Arthroplasty: A Systematic Review and Meta-Analysis. JBJS Rev. 2019 Jul;7(7):e9. doi: 10.2106/JBJS.RVW.18.00184. PMID: 31365448. https://pubmed.ncbi.nlm.nih.gov/31365448/
35. Ploeger MM, Müller NH, Wirtz DC, Kohlhof H. Adipositas in der Revisionsendoprothetik des Kniegelenks – eine systematische Literaturübersicht und rechtliche Bewertung [Obesity in Revision Total Knee Arthroplasty – a Systematic Review and Legal Assessment]. Z Orthop Unfall. 2018 Aug;156(4):436-442. German. doi: 10.1055/a-0590-5340. Epub 2018 Apr 18. PMID: 29669384. https://www.thieme-connect.com/products/ejournals/abstract/10.1055/a-0590-5340
36. Kerkhoffs GM, Servien E, Dunn W, Dahm D, Bramer JA, Haverkamp D. The influence of obesity on the complication rate and outcome of total knee arthroplasty: a meta-analysis and systematic literature review. J Bone Joint Surg Am. 2012;94(20):1839-1844. doi:10.2106/JBJS.K.00820. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3489068/
37.  Boyce L, Prasad A, Barrett M, Dawson-Bowling S, Millington S, Hanna SA, Achan P. The outcomes of total knee arthroplasty in morbidly obese patients: a systematic review of the literature. Arch Orthop Trauma Surg. 2019 Apr;139(4):553-560. doi: 10.1007/s00402-019-03127-5. Epub 2019 Feb 16. PMID: 30778723; PMCID: PMC6420900. https://pubmed.ncbi.nlm.nih.gov/30778723/
38. Lash H, Hooper G, Hooper N, Frampton C. Should a Patients BMI Status be Used to Restrict Access to Total Hip and Knee Arthroplasty? Functional Outcomes of Arthroplasty Relative to BMI – Single Centre Retrospective Review. Open Orthop J. 2013;7:594-599. Published 2013 Oct 4. doi:10.2174/1874325001307010594. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3805982/. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3805982/pdf/TOORTHJ-7-594.pdf
39. Vaishya R, Vijay V, Wamae D, Agarwal AK. Is Total Knee Replacement Justified in the Morbidly Obese? A Systematic Review. Cureus. 2016;8(9):e804. Published 2016 Sep 23. doi:10.7759/cureus.804. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5081255/
40. Chaudhry H, Ponnusamy K, Somerville L, McCalden RW, Marsh J, Vasarhelyi EM. Revision Rates and Functional Outcomes Among Severely, Morbidly, and Super-Obese Patients Following Primary Total Knee Arthroplasty: A Systematic Review and Meta-Analysis. JBJS Rev. 2019 Jul;7(7):e9. doi: 10.2106/JBJS.RVW.18.00184. PMID: 31365448. https://pubmed.ncbi.nlm.nih.gov/31365448/
41. Lash H, Hooper G, Hooper N, Frampton C. Should a Patients BMI Status be Used to Restrict Access to Total Hip and Knee Arthroplasty? Functional Outcomes of Arthroplasty Relative to BMI – Single Centre Retrospective Review. Open Orthop J. 2013;7:594-599. Published 2013 Oct 4. doi:10.2174/1874325001307010594. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3805982/. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3805982/pdf/TOORTHJ-7-594.pdf
42. Evans JT, Mouchti S, Blom  AW, Wilkinson JM, Whitehouse MR, Beswick A, Judge A. Obesity and revision surgery, mortality, and patient-reported outcomes after primary knee replacement surgery in the National Joint Registry: A UK cohort study. PLoS Med. 2021 Jul 16;18(7):e1003704. doi: 10.1371/journal.pmed.1003704. PMID: 34270557; PMCID: PMC8284626. https://pubmed.ncbi.nlm.nih.gov/34270557/.  https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003704
43. Giori NJ, Amanatullah DF, Gupta S, Bowe T, Harris AHS. Risk Reduction Compared with Access to Care: Quantifying the Trade-Off of Enforcing a Body Mass Index Eligibility Criterion for Joint Replacement. J Bone Joint Surg Am. 2018 Apr 4;100(7):539-545. doi: 10.2106/JBJS.17.00120. PMID: 29613922; PMCID: PMC5895162. https://pubmed.ncbi.nlm.nih.gov/29613922/
44. Collins JE, Donnell-Fink LA, Yang HY, Usiskin IM, Lape EC, Wright J, Katz JN, Losina E. Effect of Obesity on Pain and Functional Recovery Following Total Knee Arthroplasty. J Bone Joint Surg Am. 2017 Nov 1;99(21):1812-1818. doi: 10.2106/JBJS.17.00022. PMID: 29088035; PMCID: PMC6948795. https://pubmed.ncbi.nlm.nih.gov/29088035/. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6948795/
45. Amin AK, Patton JT, Cook RE, Brenkel IJ. Does obesity influence the clinical outcome at five years following total knee replacement for osteoarthritis? J Bone Joint Surg Br. 2006 Mar;88(3):335-40. doi: 10.1302/0301-620X.88B3.16488. PMID: 16498007. https://online.boneandjoint.org.uk/doi/full/10.1302/0301-620X.88B3.16488
46. Collins RA, Walmsley PJ, Amin AK, Brenkel IJ, Clayton RA. Does obesity influence clinical outcome at nine years following total knee replacement? J Bone Joint Surg Br. 2012 Oct;94(10):1351-5. doi: 10.1302/0301-620X.94B10.28894. PMID: 23015559. https://pubmed.ncbi.nlm.nih.gov/23015559/
47. Kunutsor SK, Whitehouse MR, Blom AW. Obesity paradox in joint replacement for osteoarthritis – truth or paradox? [published online ahead of print, 2021 Aug 27]. Geroscience. 2021;1-9. doi:10.1007/s11357-021-00442-x. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8396800/ 
48.  Flegal KM, Kit BK, Orpana H, Graubard BI. Association of all-cause mortality with overweight and obesity using standard body mass index categories: a systematic review and meta-analysis. JAMA. 2013 Jan 2;309(1):71-82. doi: 10.1001/jama.2012.113905. PMID: 23280227; PMCID: PMC4855514. https://pubmed.ncbi.nlm.nih.gov/23280227/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4855514/
49. Hainer V, Aldhoon-Hainerová I. Obesity paradox does exist. Diabetes Care. 2013 Aug;36 Suppl 2(Suppl 2):S276-81. doi: 10.2337/dcS13-2023. PMID: 23882059; PMCID: PMC3920805. https://pubmed.ncbi.nlm.nih.gov/23882059/. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3920805/
50. Gribsholt SB, Pedersen L, Richelsen B, Sørensen HT, Thomsen RW. Body Mass Index and 90-Day Mortality Among 35,406 Danish Patients Hospitalized for Infection. Mayo Clin Proc. 2021 Mar;96(3):550-562. doi: 10.1016/j.mayocp.2020.06.062. PMID: 33673909. https://pubmed.ncbi.nlm.nih.gov/33673909/
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52. Nelson CL, Elkassabany NM, Kamath AF, Liu J. Low Albumin Levels, More Than Morbid Obesity, Are Associated With Complications After TKA. Clin Orthop Relat Res. 2015 Oct;473(10):3163-72. doi: 10.1007/s11999-015-4333-7. Epub 2015 May 21. PMID: 25995174; PMCID: PMC4562915. https://pubmed.ncbi.nlm.nih.gov/25995174/. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4562915/
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59. Lash H, Hooper G, Hooper N, Frampton C. Should a Patients BMI Status be Used to Restrict Access to Total Hip and Knee Arthroplasty? Functional Outcomes of Arthroplasty Relative to BMI – Single Centre Retrospective Review. Open Orthop J. 2013;7:594-599. Published 2013 Oct 4. doi:10.2174/1874325001307010594. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3805982/. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3805982/pdf/TOORTHJ-7-594.pdf
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69. Ricciardi BF, Giori NJ, Fehring TK. Clinical Faceoff: Should Orthopaedic Surgeons Have Strict BMI Cutoffs for Performing Primary TKA and THA?. Clin Orthop Relat Res. 2019;477(12):2629-2634. doi:10.1097/CORR.0000000000001017 . https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6907311/
70. Woon CY, Piponov H, Schwartz BE, Moretti VM, Schraut NB, Shah RR, Goldstein WM. Total Knee Arthroplasty in Obesity: In-Hospital Outcomes and National Trends. J Arthroplasty. 2016 Nov;31(11):2408-2414. doi: 10.1016/j.arth.2016.04.028. Epub 2016 Apr 30. PMID: 27259393. https://pubmed.ncbi.nlm.nih.gov/27259393/
71. Ricciardi BF, Giori NJ, Fehring TK. Clinical Faceoff: Should Orthopaedic Surgeons Have Strict BMI Cutoffs for Performing Primary TKA and THA?. Clin Orthop Relat Res. 2019;477(12):2629-2634. doi:10.1097/CORR.0000000000001017 . https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6907311/
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75. Royal College of Surgeons. Is Access to Surgery a Postcode Lottery? London: RCS; 2014. https://www.rcseng.ac.uk/-/media/files/rcs/news-and-events/is-access-to-surgery-a-postcode-lottery.pdf
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78. Ponnusamy KE, Marsh JD, Somerville LE, McCalden RW, Vasarhelyi EM. Ninety-Day Costs, Reoperations, and Readmissions for Primary Total Knee Arthroplasty Patients With Varying Body Mass Index Levels. J Arthroplasty. 2018 Jul;33(7S):S157-S161. doi: 10.1016/j.arth.2018.02.019. Epub 2018 Feb 15. PMID: 29526335.
79. Raphael IJ, Parmar M, Mehrganpour N, Sharkey PF, Parvizi J. Obesity and operative time in primary total joint arthroplasty. J Knee Surg. 2013 Apr;26(2):95-9. doi: 10.1055/s-0033-1333663. Epub 2013 Jan 28. PMID: 23359399. https://pubmed.ncbi.nlm.nih.gov/23359399/
80. Ricciardi BF, Giori NJ, Fehring TK. Clinical Faceoff: Should Orthopaedic Surgeons Have Strict BMI Cutoffs for Performing Primary TKA and THA?. Clin Orthop Relat Res. 2019;477(12):2629-2634. doi:10.1097/CORR.0000000000001017 . https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6907311/
81. Woon CY, Piponov H, Schwartz BE, Moretti VM, Schraut NB, Shah RR, Goldstein WM. Total Knee Arthroplasty in Obesity: In-Hospital Outcomes and National Trends. J Arthroplasty. 2016 Nov;31(11):2408-2414. doi: 10.1016/j.arth.2016.04.028. Epub 2016 Apr 30. PMID: 27259393. https://pubmed.ncbi.nlm.nih.gov/27259393/