The good news is that studies show that common types of knee replacements can last more than 20 years. One recent study on long-term outcomes of a commonly used knee replacement found the implant to still be functioning in 96% of patients 20 years after being implanted. This is certainly one of the better reports, and other studies have not necessarily shown that level of success. However, the goal of a knee replacement should be to achieve several decades of a functioning knee.
You should remember that while some patients may have knee replacements that last several decades, other patients may require a repeat knee replacement just a handful of years after their surgery. Revision knee replacement (a second knee replacement) is a major undertaking, that often has less successful results than an initial knee replacement. On a bright note, a recent report found that only about 2% of knee replacement surgeries required a second surgery within five years of the initial knee replacement.
Factors Affecting Longevity of Knee ReplacementsMany studies have been done to determine how long a knee replacement will last. With hundreds of different types of knee replacements, and countless different types of patients, there is no rule to how long a knee replacement will last in a particular individual. Implant manufacturers are constantly striving to create a "better" implant that will last longer. Some of these implants have only been used for a handful of years, and determining whether or not they will last longer is a question only time can answer.
Some of the factors that seem to influence the longevity of knee replacement implants include:
- Age of the Patient
Younger patients require a knee replacement to last much longer. On top of that, younger patients tend to be more active. Therefore, patients who have knee replacement in their 50s or younger can usually expect to require a revision knee replacement in their lifetime.
- Patient Activities
Some activities may not be appropriate for patients with a knee replacement. While these activities may not be painful or difficult, they may be placing excessive stress on the knee replacement, causing the parts to wear out more quickly.
- Patient Weight
The more an individual weighs, the more stress that is placed on the joint replacement implant. Maintaining a normal body weight is critically important when trying to make a joint replacement last. Appropriate exercises can be helpful in maintaining a healthy knee replacement.
- Avoiding Complications
This may sound obvious, but there are some specific medical conditions that can lead to complications affecting the joint replacement. Patients having invasive medical procedures (including dental work) may require antibiotic treatment to prevent bacteria from getting into the joint replacement. Patients with osteoporosis should ensure they are being adequately treated as a fracture in the bone around a joint replacement can affect the functioning of the implant.
The Latest and GreatestOne temptation of patients and surgeons alike is to be attracted to the newest knee replacement on the market. Undoubtedly, this implant will claim to function better and last longer than other knee replacements. While these newer implants may be better, it is also important to understand they do not have long-term data on how well these implants will function over time. Ask any orthopedic surgeon about the implants they have seen come and go over the course of their career. Just because an implant is newer does not necessarily mean it is better.
I always recommend that patients and surgeons try to find an appropriate balance between modern design and not being a 'test' patient. Your surgeon can help guide you to an appropriate knee replacement that is best for you.
Buechel FF, et al. "Twenty-year Evaluation of Meniscal bearing and rotating platform knee replacements." Clinical Orthopaedics & Related Research, 388 July 2001:41-50.
Total Knee Replacement" Agency for Healthcare Research and Quality Publication No. 04-E006-2.