Being overweight places a strain on the weight-bearing joints in the body (knees and hips). We use these joints throughout the day for everyday activities like walking, standing and going upstairs and the way our anatomy works. these joint surfaces are exposed to forces up to seven times greater than our actual body weight. So, even carrying a few extra pounds can significantly increase the load on our hips and knees.
People with a higher body mass index (BMI) are at greater risk of needing a hip or knee replacement than someone with a normal BMI… and the more your BMI goes up, the higher your chances of hip and knee damage. So, maintaining a healthy body weight is a sensible precaution. If you have hip or knee osteoarthritis, it can help to reduce your symptoms and may also delay the need for joint replacement surgery.
How excess weight impacts recovery and rehabilitation
But, what about if you’ve undergone a total knee replacement, how does your weight affect your recovery and rehabilitation?
It’s an unfortunate fact that a patient who is obese (with a BMI above 30) is more likely to experience post-surgical complications (such as problems with wound healing or infection) compared to someone with a normal BMI. They are likely to remain in hospital longer after surgery and they also have a greater chance of being readmitted. People who are obese are more likely to have more than one health condition at the same time (referred to as comorbidities). For example, they might also have cardiovascular disease or diabetes and this, too, increases the risk of complications.
It’s important to point out that being overweight or obese doesn’t automatically mean you will experience worse outcomes after a total knee replacement or that you will develop complications. An individual’s recovery from surgery is influenced by a whole range of different factors including their age, lifestyle and overall state of health. However, your orthopaedic surgeon will talk to you about the risks before surgery and may encourage you to try and lose weight to increase your chances of a good outcome.
Research studies
After surgery, maintaining a healthy body weight will reduce strain on your knee as it heals and also protect your prosthetic implant against early failure. Research in this area has shown mixed results. Some manufacturers of prosthetic implants advise against using their products in obese patients due to the high risk of implant failure. However, a study published in the Annals of the Royal College of Surgeons of England in May 2016 found that a high proportion of obese patients continue to receive implants against manufacturer recommendations.
A study published in the BMC Musculoskeletal Disorders journal in 2009 explored the relationship between obesity and early failure of an implant after Total Knee Replacement surgery. The researchers looked at patients given a cemented total knee replacement between 2000 and 2005. There were 9,735 knee replacements in 8,892 patients. Of these patients, 18.9% were normal weight, 48.2% were overweight, 31.1% were obese and 1.8% were morbidly obese.
In normal weight patients, there were 36 failures out of 1840 implants (a failure rate of 1.94%). In overweight patients there were 87 failures out of a total of 4692 implants (1.85%), in obese patients there were 59 failures out of a total of 3031 implants (1.94%) while in morbidly obese patients there were four failures out of a total of 172 implants (2.3%). The researchers concluded that knee implants do not have significantly different rates of survival or perioperative complications in people who are obese compared to those who are a normal weight in the five years after surgery. The same applies to patients who are morbidly obese, although the researchers advise caution here due to the small sample of patients examined.
The benefits of maintaining a healthy body weight
However, while there may not be a statistically significant increase in the chances of implant failure following a total knee replacement if you are overweight, nevertheless, the benefits of maintaining a healthy body weight are undeniable. These include overall health benefits, a reduced risk of conditions like diabetes and cardiovascular disease, improved lung and heart fitness and lower blood pressure. It’s important, too, not to underestimate the benefits of looking and feeling better for our mental and physical health.
For advice about losing weight before surgery as well as general information on knee replacement surgery and the options available to you, contact us.
