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Current research shows that about 90% of total knee replacements will last 20 years, and 82% will still be intact 25 years after surgery. This number has steadily increased over a short period of time, and we can thank advancements in technology for that. In fact, 20 years ago the research only showed 85-90% of replacements were still intact 15 years later. While these numbers are encouraging, it’s important to recognize that your own experience may be different. One person may find they need a revision knee replacement only a few years after their initial one, while another may find their artificial knee lasts longer than 25 years.
Why would a knee replacement need to be revised? Over time, the materials that are used in a knee replacement are subject to normal wear and tear from everyday life, just like our bodies. So although the knee replacement is expected to last a long time, they are not designed to last a lifetime.
So what factors are in your control and what factors are out of your control in making your knee replacement last?
People who are 70 years and older who choose to undergo a total knee replacement are significantly less likely to need a revision surgery than people who are younger than 60 years old. The rate of a revision knee replacement for people over the age of 70 can be less than 1 in 20 people, whereas people under 60 can be as high as 1 out of 3 people. The younger a person is when getting a knee replacement, the longer the joint will need to last, ultimately making them more likely to need a revision.
It has been estimated that men under the age of 70 who undergo a total knee replacement are 15% more likely than women in the same age group to need a revision surgery. While the reason for this is not fully understood, there are theories as to why there are such discrepancies between the sexes. One suggestion considers the idea that men have differences in their knee biomechanics, which is the structure and way that the joint moves. Others suggest that women are more likely to undergo knee replacements once their osteoarthritis is more advanced, and therefore are out of alternative options. Read more about osteoarthritis and its impact on joint replacements here. Additionally, it has been mentioned that men typically have higher levels of physical activity than women, which may contribute to higher wearing down of the knee replacement. Although this may have been true in the past, current clinical experience shows that both men and women want to maintain a high level of physical activity following a knee replacement.
Have you ever noticed after many years of wearing a pair of shoes, you can begin to see the wear and tear on the bottom? This is from many hours of everyday living, where your shoes are constantly put under the pressure of your body weight. You may even notice certain areas of your shoes that wear away more because that area is loaded with most of your body weight. This is the same idea as a knee replacement - the more weight that is put onto a knee replacement, the more wearing away is likely to occur. Body mass index (BMI) is often calculated to find a healthy range of body weight for a person, specific to their height. Body mass index is a person's weight in kilograms divided by their height in meters squared or BMI = kg/m2. For example, if a person’s BMI is within the range of 18.5-24.9, then that would put them in the healthy weight category. Research has shown that a person with a BMI of 30 or higher, is at an increased chance of needing a revision knee replacement. As BMI continues to increase, so does the likelihood that a person will need a revision. Based on this research, weight loss can reduce the chances that you will need a revision after a knee replacement.
It is important to note that this blog focused on revision of knee replacements, which does not include medical complications such as infections after surgery, which is rare but could result in requiring a revision surgery.
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