Research: Knee replacement does not help many people lose weight

Ross A. Hauser, MD; Danielle R. Steilen-Matias, MMS, PA-C

Weight management, not a joint replacement. Knee replacement is not an easy way to weight loss.
Research: Knee replacement does not help many people lose weight

Many patients are under the assumption that the quickest way to attack their obesity problem is to get a knee replacement. The thinking is that if they eliminate their knee pain they will be able to exercise and lose weight. Surgeons are being told to tell patients that is not true for many obese patients.

Many patients contact us with knee problems. They tell a story that probably sounds a lot like yours:

I use to be extremely fit, worked out all the time, now I am obese

I use to be extremely fit, worked out all the time, now I am obese, I liked being very active. I ran, I hiked, I played sports, I have a home gym. I do not do any of that now. I have two knees that are letting me down. I am stuck in a cycle that I am gaining weight because I can’t exercise, and I can’t exercise because I am gaining weight. My doctors are strongly suggesting knee replacement so I can be active again and work on my weight gain. But one doctor is telling me, be careful, the knee replacement may not help me lose weight and I may even gain weight. How is that possible?

Obesity and anxiety after knee replacement

People have successful knee replacements. People can lose weight after knee replacement. People should be made aware that they can also gain weight after knee replacement. Let’s explore the science.

What are we seeing in this image?

This image is a simple demonstration of the development of a bone-on-bone knee. The more weight you have above your knee, that is in your belly and butt and thighs, the more pressure on that small area of cartilage trying to keep you from being bone on bone.

This image is a simple demonstration of the development of a bone on bone knee. The more weight you have above your knee, that is in your belly and butt and thighs, the more pressure on that small area of cartilage trying to keep you from being bone on bone.

In an August 2016 study published in the Journal of Rheumatology, (1)  doctors at the University of Texas, MD Anderson Cancer Center, suggested that following knee replacement, increasing BMI (Body Mass Index – Obesity) and rising anxiety levels and decreasing levels of positive social interactions were associated with increased patient costs (the need for continued care) following total knee replacement. The greater the obesity the greater the patient need for care (cost) following the knee replacement. What is this need? An April 2019 study from the Feinberg School of Medicine, Northwestern University published in the Journal of Clinical Nursing (2) offering this assessment:

Many patients undergoing knee replacement surgery are overweight or obese

  • “Many patients undergoing knee replacement surgery are overweight or obese. While obesity treatment guidelines encourage diet and activity modifications, gaps exist in understanding social and environmental (factors) determinants of these behaviors for knee replacement patients. Identifying these determinants is critical for treatment, as they are likely amplified due to patients’ mobility limitations, the nature of surgery and reliance on others during recovery.”

Here were the problems identified:

The problem with enablers:

  • The people who continued with weight issues following knee replacement, despite the reliance on others to help them and their own mobility issues, still had availability of unhealthy food choices. (This could be a problem of enablers).
  • Positive results were achieved with weight loss when there was an availability of healthy food, and keeping unhealthy options “out of sight,” and social support.
  • Weather was the primary activity barrier, while facilitators included access to physical activity opportunities and social support.

This study suggests that to help obese patients lose weight after knee replacement, they need a team to help them adhere to a diet.

Practitioners treating knee replacement patients would be aided by an understanding of patients’ perceived social and environmental factors that impede or facilitate surgical progress. Particularly for those directly interacting with patients, like nurses, physiotherapists, or other professionals, support from health professionals appears to be a strong facilitator of adherence to diet and increased activity.

  • This study suggests that to help obese patients lose weight after knee replacement, they need a team to help them adhere to a diet.

The hard truth: Some will lose weight because they want to, some will not because they do not want to

Here is a research paper that will probably state the obvious, especially if you are the adult child of a parent who has bad knees and a big belly or the spouse of one.

This comes from August 2020 and was published in the journal BioMed Central Musculoskeletal Disorders (3). Here are the learning points:

  • Knee osteoarthritis affects mostly older adults and its primary risk factor is obesity.
  • This study looked to understand weight-control strategies, facilitators of and barriers toward weight control in older adults with knee osteoarthritis who preferred not to undergo physician-recommended total knee replacement.

In other words, we have older people with knee osteoarthritis who have been recommended for a knee replacement. They chose not to get a knee replacement. Yet weight is a concern. What are these people thinking? That is what the researchers wanted to know.

  • Study starts with 118 patients
  • Only 1 in 4 patients, 25.4% had body weight in the normal range.
  • More than half 55.9% reported having controlled their weight.
    • Controlling weight means that they were engaged in a program to obviously, control their weight. Their most common weight-control strategies were:
      • Diet
      • Diet and exercise together
    • Their weight control program did well when the patient was motivated to have good health, wanting to improve walking or movement, perceiving that they had gained weight, wanting to look good, and advice from healthcare providers.
  • The people who had difficulties with weight control:
    • Denied that they even had a weight problem
    • They liked to eat or had difficulty on low-calorie diets
    • They did not like to be hungry.

Let’s understand this is a group of people who decided against knee replacement. About 80% or 4 out of 5 were going to try to delay or avoid the need for knee replacement by maintaining good weight and losing weight. About 1 in 5 are not only denying the knee replacement, they are denying the problem.

This last group, the deniers, are not the people we hear from. We hear from their adult children, their spouse, and sometimes even their adult grandchildren because not only is grandpa and grandma obese, but mom and dad are too and no one is doing anything about it.

Research: It is unclear whether total knee replacement facilitates weight reduction. Is the surgery a “barrier” to weight loss?

We do understand that some adult children and spouses may implore their loved ones to get a knee replacement because they “have to do something.” They are getting heavier and less mobile. In some instances, people can be “guilted,” into treatment when they perceive that they will be a “burden,” on their loved ones.

But is knee replacement an answer that will make things better or worse?

An earlier study from the Department of Preventive Medicine, Feinberg School of Medicine, Northwestern University and the Department of Exercise Science, University of South Carolina published in the journal BioMed Central Musculoskeletal Disorders (4) made these observations:

  • Most knee replacement patients are overweight/obese, yet are commonly excluded from evidence-based weight loss programs due to mobility limitations and barriers faced around the time of surgery.
  • The purpose of this study was to identify knee replacement patient preferences for weight loss programs and qualitatively understand previous motives for weight loss attempts as well as strategies used to facilitate behavior changes.

This study focused on patients who were either scheduled to have knee replacement or had one recently completed within the last 3 months (of the time of the study participation) were recruited to participate. Patients completed a brief weight loss program preference questionnaire assessing preferred components of a weight loss program (i.e. self-monitoring, educational topics, program duration).

  • Twenty patients (11 pre-operative and 9 post-operative) between 47 and 79 years completed the study (55% male, 90% White, and 85% with a BMI ≥25 kg/m2).
  • Patients reported a preference for a weight loss program that starts before surgery, is at least 6 months in duration, and focuses both on diet and exercise.
  • The majority of patients preferred to have a telephone-based program and wanted to track diet and physical activity on a smartphone application.
  • The most common motive for weight loss mentioned by patients related to physical appearance (including how clothing fit), followed by wanting to lose weight to improve knee symptoms or to prevent or delay knee replacement. Strategies that patients identified as helpful during weight loss attempts included joining a formal weight loss program, watching portion sizes, and self-monitoring their dietary intake, physical activity, or weight.

If you are reading this article, you or a loved one facing knee replacement surgery and if you are like your counterparts in this study, you want to look better than you want to your knee to work better. This would likely not be the dominating motive for someone who is self-employed or still working. As discussed above, this type of weight loss program does require a lot of costs.

Obese patients are more likely to require total knee replacement -It is unclear whether total knee replacement facilitates weight reduction

Doctors in the United Kingdom reported these findings in the journal Maturitis (5)

  • There is a proven association between obesity and knee osteoarthritis, and obesity is suggested to be the main modifiable risk factor.
  • Obese patients are more likely to require total knee replacement
  • It is unclear whether total knee replacement facilitates weight reduction
  • Surgery in obese patients is more technically challenging.
    • This is reflected in the evidence, which suggests
      • higher rates of short- to medium-term complications following total knee replacement, including wound infection and medical complications, resulting in longer hospital stay, and potentially higher rates of malalignment, dislocation, and early revision.

It is better to lose weight before total knee replacement?


Research: High patient weight is a risk factor for mechanical implant failure and some knee replacement manufacturers list obesity as a contraindication for implant use.

In another study from the United Kingdom, doctors were much more critical of putting implants into obese patients as they noted in the Annals of the Royal College of Surgeons of England.(6)

High patient weight is a risk factor for mechanical implant failure and some manufacturers list obesity as a contraindication for implant use. Doctors in the United Kingdom were amazed to find out that:

  • A total of 10,745 patients in a two year period 2012-2013 received knee or hip implants against manufacturer recommendations.
  • 16% of all obese patients) received implants against manufacturer recommendations.

Research: overweight patients are at a more than 40% greater risk and obese patients are at more than a 100% increased risk of knee replacement surgery compared to patients with normal weight


Weight reduction strategies could potentially reduce the need for knee replacement surgery by 31% among patients with knee osteoarthritis.

The simple summary of all the research listed above is this:

Doctors at Oxford University publishing in the journal Arthritis and Rheumatology (7) found that overweight patients are at more than 40% greater risk and obese patients are at more than a  100% increased risk of knee replacement surgery compared to patients with normal weight. Weight reduction strategies could potentially reduce the need for knee replacement surgery by 31% among patients with knee osteoarthritis.

The vicious cycle: I can’t lose weight because I am not mobile. I am not mobile because of my knee pain. I can’t lose weight

In our more than 27 years of experience helping people with knee pain, we have seen many patients who were overweight and considered obese. If you are reading this article, you know that there is “no magic pill,” there is “no magic formula,” to help you overcome the challenges of weight loss and knee pain. The most simple advice is that a person who desires to lose weight must burn more calories than they take in. This of course is easier said than done and the rationale behind some of the studies that we mentioned above in the tools and team required to help someone make it “easier done than said.”

We do present a lot of information on this website that may help provide an understanding of how one may lose weight with knee pain:

The evidence that cholesterol medication is sending you to knee replacement

Here is the snippet of this article: A patient comes in on a recommendation from a friend. “I am here because I have very bad knee pain . . . here is my story: I went to the doctor for my check-up. My blood work revealed slightly elevated cholesterol and I was advised that I need to take and was given prescriptions for medications that would lower my cholesterol. As a side note, I told my doctor that I did have some knee pain from a new exercise program. I said with confidence that hopefully, I can control my cholesterol with this new exercise program. My doctor said, “go easy on my knee.”

Soon after taking these new cholesterol medications, I felt a sharp pain in my knee. I wasn’t doing anything but walking to my car in the parking lot. My wife drove us home and she got me to the chair and we elevated my leg and got plenty of ice on it.

When your knee pain is coming from your unmanaged or uncontrolled Type 2 diabetes

In this article, we explore the challenges people with unmanaged or uncontrolled type 2 diabetes face with knee pain. If you are someone suffering from type 2 diabetes and knee pain, one challenge you may be facing is a diminished ability to heal your damaged knee. This non-healing will eventually lead to irreversible knee degenerative disease and the eventual recommendation to a knee replacement. Knee replacement complications in Type 2 diabetes is of course another great concern.

What is the best diet for my knee pain?

When people come into our clinic with significant knee pain, they will often ask our clinicians about what type of diet they should be on. Proper weight and proper diet are of course very important elements in healing. But how much can diet realistically do for your knee pain?

The right food stimulates healing, the wrong food can cause inflammatory reactions and make your knees feel worse. A realistic expectation one may have with food choice change is that you will probably look a little better, feel a little better, have a little more energy, and your knees may hurt less. To what degree depends on how aggressive you are with a change of diet and healing.

For more information on the different types of injections for knee pain. Please see our article: What are the different types of knee injections for bone on bone knees

If this article has helped you understand the problems of obesity and joint pain and you would like to explore Prolotherapy as a possible remedy for your joint pain, ask for help and information from our specialists

Research citations:

1 Waimann CA, Fernandez-Mazarambroz RJ, Cantor SB, Lopez-Olivo MA, Barbo AG, Landon GC, Siff SJ, Lin H, Suarez-Almazor ME. Effect of Body Mass Index and Psychosocial Traits on Total Knee Replacement Costs in Patients with Osteoarthritis. The Journal of rheumatology. 2016 Aug 1;43(8):1600-6.  [Google Scholar]
2 Hoffman SA, Ledford G, Cameron KA, Phillips SM, Pellegrini CA. A qualitative exploration of social and environmental factors affecting diet and activity in knee replacement patients. Journal of clinical nursing. 2019 Apr;28(7-8):1156-63. [Google Scholar]
3 Yeh WL, Tsai YF, Hsu KY, Chen DW, Wang JS, Chen CY. Weight control in older adults with knee osteoarthritis: a qualitative study. BMC musculoskeletal disorders. 2020 Dec;21(1):1-8. [Google Scholar]
4 Pellegrini CA, Ledford G, Hoffman SA, Chang RW, Cameron KA. Preferences and motivation for weight loss among knee replacement patients: implications for a patient-centered weight loss intervention. BMC musculoskeletal disorders. 2017 Dec;18(1):327. [Google Scholar]
5 Kulkarni K, Karssiens T, Kumar V, Pandit H. Obesity and osteoarthritis. Maturitas. 2016 Jul;89:22-8. doi: 10.1016/j.maturitas.2016.04.006. Epub 2016 Apr 11. Review. [Google Scholar]
6 Craik JD, Bircher MD, Rickman M. Hip and knee arthroplasty implants contraindicated in obesity. Ann R Coll Surg Engl. 2016 May;98(5):295-9.  [Google Scholar]
7 Leyland KM, Judge A, Javaid MK, Diez-Perez A, Carr A, Cooper C, Arden NK, Prieto-Alhambra D. Obesity and the Relative Risk of Knee Replacement Surgery in Patients With Knee Osteoarthritis: A Prospective Cohort Study. Arthritis Rheumatol. 2016 Apr;68(4):817-25. [Google Scholar]

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