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BMI Does Not Affect Outcomes in Knee-Replacement Surgery



sharma-obesity-knee-arthtoplasty2One of the most pervasive “myths” amongst orthopaedic surgeons is that higher BMI is a contraindication to knee-replacement surgery.

Regular readers, however, will perhaps previous posts on this issue, suggesting that BMI is largely irrelevant in terms of outcomes and benefits for obese patients requiring knee replacements.

This previous finding is further supported by a new paper by David Murray and colleagues from The University of Oxford, UK, published in KNEE.

The researchers prospectively examined the impact of BMI on failure rate and clinical outcomes of 2,438 unicompartmental knee replacements in 378 patients with a BMI less than 25, 856 patients with a BMI 25 to 30, 712 patients with a BMI 30 to 35, 286 patients with a BMI 35 to 40, 126 patients with a BMI 40 to 45 and 80 patients with BMI greater than 45.

At a mean follow-up of 5 years (range 1–12 years) there was no significant difference in the Objective American Knee Society Score between BMI groups.

Although there was a slight trend to decreasing post-operative function scores with increasing BMI, patients with higher BMI had lower scores prior to surgery. Thus, overall higher BMIs were associated with a greater change in functional scores.

Thus, this study, further confirms the notion that obese individual have as much (if not more) to benefit from knee replacement surgery with little evidence that initial BMI adversely affects outcomes.

For clinicians this finding means that there is little evidence to deny knee replacement surgery to individuals with higher BMI levels or require that these patients lose weight prior to surgery.

If you have experience (positive or negative) with knee replacement surgery in overweight and obese patients, I’d like to hear from you.

@DrSharma
Edmonton, AB

19 Comments

  1. Loved the article. I have seen both sides of this one. I am an primary care RN working with a focus in Weight Management. This has always been a question of mine. I feel any surgeries that can be performed to assist the obese patient in managing chronic pain is necessary. Two I see most are knees and breast reduction (neck and shoulder issues). I feel these should be seriously considered despite BMI results. I have two clients in particular that have had excellent recoveries from knee surgeries. Male 66 years old, BMI 56. Better than text book recovery. Impressive mobility. It went so well the surgeon was more than happy to perform the second knee replacement within the calendar year. Both knees, great success. Female 50 years old, BMI 53. Post-op infection slowed her slightly, maybe 3 days. It was caught quickly and she had a great recovery also. I truly feel if more of our obese patients were treated surgically the benefits to their mental and physical health are immeasurable. It helps them see they are worth the effort.

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    • I had miniscus disc surgery in left knee in 2006. And now have osteoarthitis. My right knee also now. Dr.will not do surgery due to obesity. Help;

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    • Hi I’m a 47 yr old woman with chronic osteoarthritis in all my joints I need a total knee replacement on my left knee urgently as I have zero cartilage left and I’m almost completely imobile with it my orthopaedic surgeon says I must lose 155lbs before he will do the surgery how am I meant to lose that much weight when I can’t walk or exercise and the reason I can’t walk is I gained so much weight due to my mobility getting much worse I intend to show this information to my surgeon on my next visit but I’m not hopeful he will help me I’m at my wits end trying to cope daily and being totally housebound

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    • It’s been two years since 6 different surgeons said I had to have less then a 46 BMI. How can you exercise and lose weight when you can’t walk. My quality of life is zero. I am just about in a wheel chair cause my knee feels like it is crumbling under me. I have hardly seen my new grand kids. I had my right knee done in 2007 and at that time my left knee was worse but my right was giving me more pain so they did the right. I have been on a 800 calorie diet less then 20 carbs AND HAVE ONLY LOST 22 pounds. There has to be someone to do my knee. Once I can walk I will get this weight off. I am being denied to have a happy life

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  2. We humans must make good replacement knees, but how about for the cause of knee surgery vs obesity?

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  3. I am considered obese, i have had a total knee replacement. Im just coming into my sixth week now. I am still using crutches to walk, i think my mobility will take a bit longer. Occassionly i will walk without aids around home. But exercises are good, no complications have occured, i am pleased with what my surgeon has done. One knee on the mend and one still to go. Looking forward to walk with my grandchildren without the pain of arthritis in my knees. I am a 58yr old female.

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  4. Obesity is the major factor of knee joint pains and the very cause for my aunt to undergo a knee surgery. She is now feeling much better with the treatment and surgery. She is able to walk without the help of any aids after six months.

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  5. I am glad to hear this. I am in a program for weight loss surgery, and my knees are so bad, I am no longer able to productively exercise due to the extreme pain.
    I have 7lbs to go to reach my pre op weight for bypass, but I feel I would be better off to have the TKR first and then continue on my journey for the bypass.

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  6. Was just out of the service in 2011 or 2012 at 47 and was learning to run again after back and ankle surgery. I injured my right knee and sought treatment at the VA. After several MRIs and a standing Xray over several months it was determined to be a torn maniscus, torn ACL, PCL,MCL, and arthritis.Of course the VA takes it’s sweet time, meanwhile Im gimping around, loosing mobility, gaining weight….and when I finally convince them I need a new knee, they fall back onto their favorite excuse…Your BMI is too high. Yeah, I suppose so. Been 3 years since the injury, I’m over 40lbs heavier, been farmed out to the VA fat boys club, pain management club, diabetes club, etc. Oh and the “experimental pain drug club” because we dont give vets actual pain meds like a real doctor or dentist would.I will die much sooner due to stress of the pain, the loss of mobility, and the overall health effects of lost mobility, and for what? A lie.

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  7. I’m a 43 year old female with a BMI of 45. I’ve had 7 knee surgeries for everything from torn meniscus(lateral & medial), torn ACL, torn MCL, bone spurs in the knee joint and so on. I was hit by a car when I was 12 years old, so thats where the problems started. I recently (October 2014) had ACL reconstruction surgery done using a cadaver ligament and 7-weeks after that surgery my knee became infected. They did surgery on it again, and approximately 6-weeks later the test results came back and they said that the infection that I had in my knee was TB, yes I said TB as in Tuberculosis. So I’ve been undergoing treatment for the TB since February. So, the infection has destroyed the new ACL,I have another torn meniscus and so much arthritis that I can barely walk even with a walker. I’ve gained because I can’t get any exercise because I can’t walk, so they tell me today that I need TKR right away or I’m going to be confined to wheelchair, but that my BMI is too high and if they were to do surgery now at my current size (5’7″/298lbs) that it would be all for nothing because the new knee would fail. How am I supposed to exercise and lose weight if I can’t even walk?

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  8. I had a horseback riding injury in 2013. My BMI is 31. My blood pressure, glucose, and cholesterol are great. I have no illnesses other than depression from pain as a direct result of the injury not receiving proper treatment. Despite MRIs showing damage, I was told I was not a candidate for surgery (no reason given) and to do PT by a world renowned medical provider based in Minnesota. I was in PT for two years. Since that time, my spine, the knee on the same side, and my other hip have degeneratd. I just learned that the previous MRIs were ordered to specifically avoid imaging of the hip socket. Finally, in late 2015, the hip socket was imaged. The entire labrum is torn out and the the gluteus minimus and medius tendons have high grade tears. There’s no doubt that eveident-based medicine was thron out the window for no other reason than BMI. I have a permanent disability because the doctor didn’t like my body shape. Frankly, this behavior should be criminal.

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  9. I am a 44 yr old male,,,10 years of football,,2 tours in army in dessert storm,,, had left tkr nov,3 2015,,,,,right tkr being done dec 28 2015. I was told my bmi was 48 until, a “fat check” was done and resulted to be 32 bmi my weight is 347 lbs.im 6’1 tall if the bmi calculator is done with the weight of 250 ish it would say im 80 to 90 lbs over weight,,,,i have extreme osteoarthritis in both knees. The surgeon that did the left actually made life alot better for me so hes doing the right,,,,,once the swelling and tenderness goes down life should be great again,,,,peopld should never give up hope,,,,and thank you for a GREAT REALITY on us larger patients and the reality of tka…

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  10. I am considered obese and have recently had the misfortune of having to under a pretty intense knee replacement. I had to undergo some reconstructive surgery in order to correct a severe trauma. The whole process leading up to the surgery was traumatic for obvious reasons. I don’t want to go into too much detail but during my surgery, my team used a FAW blanket called the Bair Hugger and it helped so much with my post surgical recovery. I credit my super quick recovery to the blanket. Here are some facts about the system http://www.fawfacts.com

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  11. I have a bmi of 43 45. Where do you find a surgeon that will do the knee replacements? They all say
    I have to loose weight before they will touch me. Help I am in pain.

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  12. I am a 48 year old female 6’2 and both my knees need replacement, but my othropedic Dr. will not perform the survey because my BMI is 50.1, its devasting not to be able to walk or stand longer than 10 minutes. I no longer have a social life due to my severe pain when moving. No wonder I have gained 20 pounds in the last year, I can’t move without pain. My right knee has needed the replacement since 2013, now it has caused my back to hurt on right side and siatictia hurts in both legs at same time. I just received my degree and I have been looking for a job, but hard to do, when you can’t just apply for anything. When I do get an interview, I don’t think people want to hire because of my size.

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  13. I’m in the same boat BMI wise. I’m stuck at 6 lbs over the doctor’s 40 BMI limit. I’ve been on a weight loss program for over two years. I’ve had several orthopedic surgeries in the past and I have always tolerated them well. I had a knee replacement only 2 years ago. My opposite knee went bad during that recovery and now I’m stuck unable to exercise again, so I’m going nowhere with my weight loss. Can’t wait any longer. Doctors at Kaiser still refuse to see me even though I’m so close at 40.3. This is ridiculous. I’ve read many articles rebuking their claim that over 40BMI makes this surgery more risky. I really do believe that if they didn’t have so much business (wait time at Kaiser last I checked is 3 months to get scheduled with at least a 3 month wait after that. Previously being very active and social, I’ve grown depressed and withdrawn. I’m still relatively young at 66 having just retired. I see nowhere to turn away from what’s turning out to be a dismal retirement.

    Kaiser facilities don’t have enough available surgeons to keep up with demand, and this is why I have to suffer through my retirement and be treated like a second class citizen.

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  14. I’m a veteran and I’ve gone from needing knee replacements (2), and being able to walk to being in constant pain. I use a cane or walker around the house, but if I have to go out I take my wheelchair now. The VA doctor said lose 50lbs after I did they said do 30 more . This has gone on 4 years ! I can’t walk, I don’t live outside my house anymore , all because I weigh 290 lbs.

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  15. I also have a high bmi. I need surgery in both knees and hip. My doctor says I need bariatric surgery before my joints get replaced. I am confused. To me surgery is surgery. How is it they would be more inclined to to bariatric surgery, rather than the joint surgery. Lack of mobility has contributed to my obesity problem.

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  16. I am a 61 year old woman with cervical and lumbar spine problems and osteo arthritis in both feet,permanent nerve damage in both hands,and both knees have been bone on bone for over two years. I weigh in at 259lbs and like many of you have been told my bmi is too high for any kind of knee surgery (and let’s face it people it’s just another way of calling us fat to our faces).I have had two foot surgerys and two cervical spine surgerys with no problems but when it comes to knee it’s a no go so I get to live in pain of O was a cognitively put me down as that would be tenth most humane thing to do go figure!!!!

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