Many patients do not lose weight after knee replacement

Many total knee replacement patients are overweight or obese. There is a thinking among many that after the knee replacement, their  physical activity levels and weight will improve. This does not appear to be true for some as research points out. In many knee replacement patients, weight loss does not occur. 

I recently read 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.


A June 2022 study (11) noted that “obesity is one of most discussed factors when assessing prosthetic knee surgery outcomes. Prior to the procedure, most patients perceive that their excessive weight is secondary to the low level of activity due to limiting knee pain.” In this study 247 patients who undergone total knee replacement from January 2018 to January 2019 were followed to see if a significant change in weight was observed. Significant change was considered anything above or below 5% of the pre-operative weight.

  • Three groups were established based on a change in weight:
    • loss of more than 5%,
    • those who did not pass above or below 5% of their initial weight and
    • increase of more than 5%.
  • Follow-up was carried out at 12 months

Among the total population, 17 (6.9%) lost weight, 168 (68%) did not have a change, and 62 (25.1%) increased weight at one year follow-up. Conclusion: Patients who undergo total knee replacement do not lose weight one year after surgery.

Many people who give up sports before the knee replacement do not return to them

This research was supported by a June 2020 paper (2) which concluded: “Most patients who stopped participating in sport activities prior to surgery, however, do not seem to reinitiate their sport activities after surgery. As such, to achieve the full benefits out of knee replacement, clinical guidelines and strategies aimed to keep patients capable and motivated to participate in sport activities until close before and after surgery are warranted.”

It’s the weather, I don’t want to go to the gym

An April 2020 report (3)  suggested that people with advanced osteoarthritis found it difficult to continue walking or sports with seasonal weather change. Other factors included dislike of gyms, concern of walking on hardwood floors, etc.”

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 (4) 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. (5)

The second knee replacement surgery in the obese patient

A February 2022 study (9) examined the postoperative outcomes of obesity and morbid obesity patients after revision total knee arthroplasty. An estimated 605,603 revision total knee arthroplasty surgeries were included in this analysis.

Morbidly obese and obese patients were at significantly higher risk for any complication than not obese patients. Patients with morbid obesity were associated with an increased risk of any, hematoma/seroma, wound dehiscence, postoperative infection, pulmonary embolism, and postoperative anemia complications and a lower risk of gastrointestinal complications when compared with not obese patients. Morbidly obese patients had a significantly longer length of stay than both obese and not obese patients, while no significant difference in length of stay was observed between obese and not obese patients.

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,(6) 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.

Bariatric Surgery before knee replacement

A March 2019 study (10) examined the controversies surrounding the risks of subsequent total joint arthroplasty with and without previous bariatric surgery. In this paper, a total of 9 studies with 38,728 patients were included. Overall, medical comorbidities were higher in the bariatric surgery group compared with the control morbid obesity group before total joint arthroplasty. This paper revealed that bariatric surgery prior to total joint arthroplasty was associated with reduced short-term medical complications, length of stay, and operative time. However, bariatric surgery did not reduce the short-term risks for superficial wound infection or venous thromboembolism, and the long-term risks for dislocation, periprosthetic infection, periprosthetic fracture, and revision. Subgroup analysis identified a significant reduction in the risk of short-term periprosthetic infection in the bariatric surgery group after total knee arthroplasty, but not after total hip arthroplasty.

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 (7) 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.(8)

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.


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 Konings MJ, De Vroey H, Weygers I, Claeys K. Effect of knee arthroplasty on sports participation and activity levels: a systematic review and meta-analysis. BMJ open sport & exercise medicine. 2020 Jun 1;6(1):e000729.
3 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.
4 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.
5 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.
6 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.
7 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/
8 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.
9 Hussein IH, Zalikha AK, Tuluca A, Crespi Z, El-Othmani MM. Epidemiology of Obese Patients Undergoing Revision Total Knee Arthroplasty: Understanding Demographics, Comorbidities, and Propensity Weighted Analysis of Inpatient Outcomes. JAAOS Global Research & Reviews. 2022 Feb;6(2).
10 Li S, Luo X, Sun H, Wang K, Zhang K, Sun X. Does prior bariatric surgery improve outcomes following total joint arthroplasty in the morbidly obese? A meta-analysis. The Journal of arthroplasty. 2019 Mar 1;34(3):577-85.
11 Coelho A, Leal-Blanquet J, Sánchez-Soler JF, Torres-Claramunt R, Hinarejos P, Monllau JC. Patients lose weight after a total knee arthroplasty: myth or reality?. International Orthopaedics. 2022 Mar 29:1-6.




Do You Have Questions? Ask Dr. Darrow

Most Popular
Skip to content