Myths of Knee Replacement Surgery

Knee replacement surgery is one of the most common surgical procedures performed by orthopedic surgeons, and a standard treatment for advanced arthritis of the knee joint. Once you have made a decision to proceed with knee replacement, you will undoubtedly hear from friends and family about their experience with this surgery. As we learn more about improving results and enhancing safety with this surgery, there are details that may change about the process of a knee replacement.

A friend who had knee replacement 20 years ago may have had a very different experience then you would have today. Here we review some of the myths of knee replacement, and what we have learned over time. I can assure you, that details will continue to change, and the process of knee replacement will look different 20 years from now. However, these are some of the shifts that have been made and why we no longer perform knee replacement exactly the same as in the past.

That's not to say that surgeons a few decades ago had it all wrong. In fact, it is surprising how well the early versions of knee replacement functioned, and remarkable how much they look like modern knee implants. While surgical techniques and rehabilitation plans have been refined, much of the work of performing a knee replacement looks very similar to years and decades in the past. There have been refinements, and this is where some of these myths come in to play. Learn about some of the changes in recommendations that have taken place over the last few decades.


Myth: You Should Donate Blood Before Surgery

blood in bags


The first shift in knee replacement is that patients seldom donate their own blood prior to surgery. It used to be the case where it was common for people to donate one or two units of blood preoperatively so that blood could be available if needed after surgery. The reason this was attractive was that there is a theoretically small risk of disease transmission (such as HIV or hepatitis) by using your own blood.

In reality, the risk of disease transmission is very small, and the risk of contamination of blood products may actually be higher when donating your own blood. Furthermore, the process of donating blood causes a significant drop in blood counts, making people more likely to be anemic. Because of this, not only do people who donate their own blood have a much higher chance of needing their own blood given back, they actually have a higher risk of also needing an additional transfusion. In general, it is not recommended to donate your own blood before knee replacement surgery.


Myth: Delay Surgery as Long as Possible

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The second myth is the idea that surgery should be delayed as long as possible. While there are potential problems with doing surgery on someone too young or without advanced arthritis, there is also not a need to delay surgery until a time that normal daily functions become difficult or impossible.

Knowing when to have knee replacement surgery is a difficult question for both patients and doctors trying to arrive at the best outcome. Every individual has a different perception of pain and disability, and knee replacement may be a treatment that can help some tremendously, while it may not be beneficial for others. More data is being gathered to determine how to best advise patients on when to proceed with the surgical treatment of knee arthritis.

That said, there are downsides to delaying knee replacement too long. One of the most important predictors of both the function and mobility of a knee replacement is the function and mobility of the knee prior to surgery. People who have very stiff, very weak knees before surgery are unlikely to recover as much function or motion as people who have stronger and more flexible knees.

There is also a concern that as people have worsening symptoms of arthritis in their joints, they may become more sedentary. This can lead to weight gain and other medical issues including poorer exercise tolerance, diabetes, and other concerns. Not allowing the body to become de-conditioned can help to improve the results from knee replacement surgery.


Myth: A Minimally Invasive Surgery Is Better (or Worse)

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This is a controversial statement because no one can really tell you what it means, but allow me to explain: There has never been an agreement on what defines "minimally invasive knee replacement." I have seen some surgeons who advertise this who seemingly perform a very standard knee replacement. Conversely, I have seen surgeons who make no such claims of minimally invasive but have outstanding results from surgery with very minimal, less-invasive surgical procedures.​

The point is, anyone can say that what they do is minimally invasive. However, that really doesn't mean a whole lot in and of itself. All joint replacement surgeons strive to place a well-functioning implant with as little unnecessary soft-tissue damage and dissection as possible. There are some techniques that are proposed to possibly limit the amount of soft-tissue damage, but there is little agreement on how much these matter.

The reality is, the most important aspect of knee replacement is not the size of the scar but the quality of the surgery. I certainly feel the most important aspect is to find an experienced surgeon, with a record of excellent outcomes. If you have questions about their specific surgical techniques, it is reasonable to ask, but I caution you that anyone may claim their techniques are minimally invasive. That may not mean too much.

There is no clear consensus that performing a knee replacement surgery through any minimally invasive approach leads to better long-term results, whereas there is abundant research to support the notion that having a well-positioned and aligned knee replacement implant is critical to a successful outcome. The bottom line—don't sacrifice the quality of the surgery for a smaller scar!


Myth: Going to Inpatient Rehab Means Better Therapy

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In the earlier years of knee replacement, people would come into the hospital the day before their surgery. After surgery, they might spend a week or longer in the hospital, before being transferred to a post-acute care (rehab center or nursing home) facility for further recovery. My, how times have changed!

Today, some surgeons are experimenting with outpatient joint replacement, where people return home as early as the same day as their surgery. This is certainly not the norm, but many patients are returning home within a few days of surgery, and the use of post-acute care rehabilitation is plummeting. The percentage of people returning home after surgery has gone from about 15 percent in the late 1990s to well over 50 percent now.

There are several reasons why going home may be better, among them being that people who return home seem to have fewer complications. A 2016 study, which evaluated specific factors that can be used to predict which patients are most likely to be readmitted to the hospital after knee replacement, found that discharge to an inpatient rehab facility made this more likely.

Many surgeons prefer home and outpatient rehab and are less concerned about the likelihood of healthcare-acquired infections that can occur in hospitals, nursing homes, and rehab facilities. In addition, the cost of care of a patient returning home is much less, so there is significant economic pressure to try to get patients home rather than to an inpatient facility.


Myth: Bending Machines Speed Recovery

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For more than a decade, mostly in the 1990s, the use of machines called CPM, or continuous passive motion was popular. These machines were placed in the bed of a patient who had a recent knee replacement, and while lying in bed, it gradually bent the knee up and down.

This makes a lot of sense; one of the most significant challenges of knee replacement rehabilitation is the recovery of motion of the knee joint. Early movement is probably the most important means to ensure recovery of motion. By placing patients in a CPM, the hope was to get a jump start on one of the most challenging aspects of rehab.​

In fact, there are early results were encouraging. The data suggested that in the days and first weeks following knee replacement surgery, people who used the CPM device did have slightly improved range of motion. However, within 4 weeks of surgery, there was no statistical difference between people who used the CPM machine and those who did not. Furthermore, other measures of recovery beyond the range of motion seemed to suggest that those who used the CPM lagged behind.

The reality is that data clearly shows that for a standard knee replacement, these don't matter. In fact, they may actually slow things down by limiting the number of times people actually get up and out of bed, a much more important aspect of the early phases of rehab from knee replacement.


Myth: No Flying for 3 Months

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One of the most important aspects of improving the results of knee replacement surgery is avoiding complications associated with this procedure. One of the complications that many people are concerned about is a ​blood clot. There are numerous treatments and steps taken to prevent a blood clot.

In addition, surgeons will try to limit other factors that can increase the chance of blood clot. One of those risk factors is air travel. It is well known that prolonged air travel can increase the likelihood of blood clot. For this reason, many surgeons will advise against any air travel for 3 months (or sometimes longer) after surgery.

The reality is that studies have not found air travel, especially in shorter flights (under 4 hours), to increase the chance of blood clot in people who have recently had a knee replacement. In fact, one study examining patients who flew home from surgery (within days of their procedure), there was no difference in the chance of blood clot.

The authors of this study still recommend all the standard precautions (medicine to thin blood, early and frequent mobilization, compression socks), as well as limiting the duration of flights, but they did not find that flying needed to be avoided altogether. In addition, there may be other factors that contribute to an increased risk of blood clot, so before considering air travel after knee replacement surgery, you should discuss this with your doctor. However, most doctors are becoming more liberal with their recommendations restricting air travel following surgery.

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