Are Heavier Patients More Likely to Have a Knee Replacement Revision?

04/09/2019

It's a myth to believe that every injection of PRP or stem cells will help 100% of the patients with knee arthritis. In fact, there's a failure rate with all of these technologies. So if you do need a knee replacement, what might determine if that's a success or failure? Turns out weight is one thing to consider. 

Knee Arthritis and Knee Replacement

Knee arthritis pain and dysfunction is the main reason patients decide to pull the trigger on a knee replacement. Knee arthritis occurs when the cartilage and bone in the knee breaks down, typically due to years of wear and tear. Most physicians will help patients manage their knee arthritis, often for years, by attempting to relieve the pain with conservative measures like physical therapy or with more dangerous nonsteroidal anti-inflammatory drugs (NSAIDs) or, as time goes on and those things no longer provide enough relief, even high-dose steroid injections that are likely only killing off more cartilage in the process.

Finally, when all of these measures have been exhausted and the knee arthritis has advanced even further, doctors start suggesting knee replacement. This procedure involves completely amputating your knee joint, cutting off the end of the long bones in the leg, and replacing these structures with an artificial joint. So how well does this procedure work? Turns out not as well as we once believed.

One of the reasons we may be seeing poorer results in knee replacements was delineated by a large government-funded study on the procedure. It basically found that the procedures work well if they're used in the traditional population for which they were designed: the elderly who can barely get around due to knee pain. The positive results get washed out if knee replacement is used in younger patients with less pain and more function. 

The Higher the BMI, the Greater the Knee Replacement Revision Risk

First, what does revision mean? It's a medical term that means having to redo a joint replacement. This is a big surgery, as it means that the existing prosthesis is removed and a new one is inserted in its place.

The new study of nearly 19,000 patients investigated whether or not body mass index (BMI) had any impact on complications and revisions following knee replacement or hip replacement. The higher the BMI, the more overweight the patient. So this study asked the question of whether being obese increased the odds of the surgeon having to redo the joint replacement at a later date.

The results? Joint replacement increased as BMI increased in the knee replacement patients. One analysis made a significant association between morbid obesity and increased revision rates for hip replacement patients; however, a second analysis did not show a significant association between BMI and hip replacement revision. Researchers concluded that there was a stronger association between BMI and knee replacement revision than hip replacement revision.

What does this mean exactly? The more obese you are, this study suggests, the higher your risk for knee replacement revision and complications after surgery. Since the primary reason patients undergo a knee replacement is for knee arthritis, let's review what we know about obesity and knee arthritis.

What Else Do We Know About Knee Arthritis and Obesity?

This new study may show the effect obesity has following a knee replacement, but can obesity actually increase the risk of needing a knee replacement in general? I covered a study a few years ago that found that knee replacement risk doubles for every 20 extra pounds gained. So not only is obesity linked to complications and revisions after knee replacement, but it's also linked to an increased likelihood of having the initial knee replacement in the first place.

How does that work? One way is obvious and the other is not as obvious. More weight places more stress on the cartilage. However, the extra weight also messes with the chemical environment in the knee caused by instability in blood sugar.

What Can You Do To Help?

One way to help is to lose weight. One of the more interesting approaches to this that's got a lot of scientific horsepower is a Fasting Mimicking Diet or FMT. This is where you drop your calories to about one thousand or less for a few days a month. There's even a company started by the doctors who did the research that makes this diet as easy as eating only the stuff they send in the box for 5 days a month.

The upshot? If you absolutely need a knee replacement, consider losing weight. It's awful to go through the trauma of the initial procedure and then find out that they need to rip that device out and put in a new one. Hence, do your part in making the surgery a success!

Source: https://regenexx.com/blog/are-heavier-patients-more-likely-to-have-a-knee-replacement-revision/