Marc Darrow MD,JD

The majority of total knee replacement patients are overweight or obese and physical activity levels and weight do not appear to change in a high proportion of patients after knee replacement

I was reading a study in the journal Disability and rehabilitation.(1) It was led by Northwestern University. It talked about the weight problems people have after they had total knee replacement and the continued problems the patients had in the inability to losing weight despite the new knee.

This study may come as a surprise to many who think that a knee replacement will help them shed pounds put on by the immobilization caused by their long battle with degenerative knee disease and knee pain.

I want to give some of the learning points here directly from the research so you can get the story directly from the people in the study.

  • “Both before and after total knee replacement, patients reported that knee pain, loss of range of motion, stiffness, swelling, inability to stand for a long period of time, loss of strength, fatigue and fear of falling interfered with their ability to be more physically active.”
  • Patients, before their surgery, discussed limitations in physical activity related to knee pain, such as an inability to bend down to do yard work and issues with balance.
  • “One patient discussed how activity led to pain, ultimately making her avoid any activity: “the reality is if I walk for 30 to 45 min, then I have a burning sensation in my knee. I’m also always conscious that my kneecap could be slipping out. I worry about that. Those are definitely limitations that don’t allow me to work out”
  • “Several patients reported difficulty in engaging in physical activity due to having lower levels of fitness, not enough stamina, and getting fatigued quickly. “I still have to get some more muscles in my leg because I knew when I was not walking for two years before the surgery I was losing a lot of ability to walk and every-thing else. So now it’s hard to walk because I didn’t walk in two years” (This came from a 78 year old male patient after his knee replacement).

The knee replacement did not provide enough motivation to lose weight:

  • “Besides pain and physical limitations, lack of motivation and mood interfered with activity. One patient described her mood after surgery as an obstacle to getting to the gym: “many days where I was just like disgusted with everything and just sat on the sofa all day … ”

  • Another patient mentioned that the biggest challenges with being active were related to, “attitude and knee. Bad knee and attitude where, my depression limits me … If I don’t have a meeting to go to then I have a hard time getting out of bed … ”

It is interesting to note that this research pointed out: The majority of total knee replacement patients are overweight or obese and physical activity levels and weight do not appear to change in a high proportion of patients after knee replacement

Not only does knee replacement not help some patients lose weight, it causes them to gain it

This is research from Dr. Daniel Riddle Virginia Commonwealth University in the medical journal Arthritis care and research (2) This study was used as a basis for the above study.

“Patients who undergo knee (replacement) are at increased risk of clinically important weight gain following surgery. Future research should develop weight loss/maintenance interventions particularly for younger patients who have lost a substantial amount of weight prior to surgery as they are most at risk for substantial postsurgical weight gain.”


  • Patients are at risk to GAIN weight after knee replacement
  • Patients who lost weight before the knee replacement, especially the younger ones, are at a greater risk to gain substantial weight after the knee replacement.

In the 5 years that separated the two studies, the problem remains. It should also be noted that two of the patients referenced in the first study were young women in regard to knee replacement age 50 and 55 years old.

54% of the patients presented weight gain after knee replacement

Let’s not rely on one study, let’s explore further with researchers in Brazil. Publishing in the Brazilian journal of orthopedics:


  • In this study researchers observed no significant reduction in body mass after knee replacement surgery, and 54% of the patients presented weight gain.
  • Patients who underwent Total Knee replacement did not obtain a significant reduction of Body Mass Index after the surgical procedure. (3)

If weight is a problem before knee replacement, weight will be a problem after knee replacement

We see many patients who struggle with weight. Being obese and overweight is an extraordinary difficult challenge to overcome, especially when you have limited mobility before knee replacement and limited mobility during rehabilitation. Add to the rehabilitation, which is already hard enough on its own, other complications that may arise. All this makes weight loss after knee replacement that much more of a challenge.

Medical engineers in China presented a study that is of concern to the overweight recipient of a total knee replacement. In this research in the Journal of healthcare engineering,(4) they noted that more weight meant a  higher stress on the knee replacement and this indicates an increased risk of femoral component migration and accelerated wear and tear. This means the possibility of a second surgery to fix the hardware and the bone.

How do we explain this? Most patients say that they get knee replacement to reduce pain and increase function. Research says patients post-knee replacement likely not to improve activity levels.


An April 2018 study in the Journal of orthopaedic translation (5) made this assessment:

“It is well documented that patients with knee osteoarthritis suffer from reduced physical function and that function of the affected knee is improved after knee joint replacement. However, it remains uncertain whether patients with KOA are less physically active than healthy people and whether patients increase their level of physical activity after surgery to a level comparable with that of healthy people. The aim of this study was to examine whether patients with knee osteoarthritis are less physically active than healthy participants and whether patients who have undergone knee joint replacement show an increased activity and achieve the same level of physical activity as healthy participants 5 years postoperatively.”

The results: “Patients with knee osteoarthritis and knee joint replacement showed no significant reduction in number of daily step counts and transfers from sitting to standing position when compared with matched healthy controls. However, the number of short walking bouts was reduced in patients with knee osteoarthritis and by twice as much in patients with knee joint replacement. This indicates that knee osteoarthritis and treatment with knee joint replacement hardly affect health-related general activity but do affect specific physical activity behavior potentially indicative of knee osteoarthritis or post-knee joint replacement functional limitations.”

How can this be? Less activity after knee replacement?

So now we come upon this research published in the World journal of orthopedics. Here are the highlights:

  • The investigation of physical activity following total knee replacement found several studies that suggest physical activity for patients is at below pre-surgical levels.
  • Daily physical activity for patients following total knee replacement may fall short and does not meet recommended daily amounts for health maintenance and/or improvement.(6)

The take home message

Research tells us that there are no easy answers to losing weight and increasing physical activity, and that patients should not be lead to believe that knee replacement is the easy way to achieve these goals.

Will stem cell therapy help me lose weight?

There is no audio in this video.

I know what some of you are thinking, if knee replacement will not help me lose weight how can our stem cell therapy treatments help you lose weight? Most people who come into our office know they are overweight and know they need to lose weight.But they are also plagued by knee instability problems like those mentioned by the study patients above. Stem cell therapy addresses the knee weakness and knee instability immediately. A good diet plan can address the weight loss simultaneously to the stem cell treatments. In many patients we get that jump start of weight loss and reduced pain quickly, enough to help many create the “momentum and motivation,” they need to heal their problems.

Do you have questions? Ask Dr. Darrow

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1 Pellegrini CA, Ledford G, Chang RW, Cameron KA. Understanding barriers and facilitators to healthy eating and physical activity from patients either before and after knee arthroplastyDisabil Rehabil. 2017;40(17):2004-2010.
2 Riddle DL, Singh JA, Harmsen WS, Schleck CD, Lewallen DG. Clinically important body weight gain following knee arthroplasty: A five-year comparative cohort studyArthritis care & research. 2013;65(5):669-677. doi:10.1002/acr.21880.
3 Schwartsmann CR, Borges AM, Freitas GLS de, Migon EZ, Oliveira GK de, Rodrigues MW. Do patients lose weight after total knee replacement? Revista Brasileira de Ortopedia. 2017;52(2):159-163. doi:10.1016/j.rboe.2017.01.003.
Wang C, Guo Y, Shi J, Chen W. A Numerical Investigation into the Effects of Overweight and Obesity on Total Knee ArthroplastyJ Healthc Eng. 2017;2017:1496379.
5. Daugaard R, Tjur M, Sliepen M, Lipperts M, Grimm B, Mechlenburg I. Are patients with knee osteoarthritis and patients with knee joint replacement as physically active as healthy persons?J Orthop Translat. 2018;14:8-15. Published 2018 Apr 3. doi:10.1016/
6 Paxton RJ, Melanson EL, Stevens-Lapsley JE, Christiansen CL. Physical activity after total knee arthroplasty: A critical review. World Journal of Orthopedics. 2015;6(8):614-622. doi:10.5312/wjo.v6.i8.614.

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