How long does a knee replacement last? What studies say. -

Have you had a knee replacement, or are you planning to have one?

In this article I will answer the most common questions asked about the lifespan of a knee replacement and what can be done to extend its lifespan.

I will rely on scientific publications on the subject matter.

Happy reading!😃

Any questions? remarks? Let’s meet in the comments section at the end of this article.🙏

Last updated: Aug 2024. Written by Juliet Semakula a diagnostic radiographer

▶️Basic knee anatomy compartment:

Before I delve into the subject matter let’s first examine the knee joint compartment.

In general, there are three types of knee replacement. To understand how they differ, it is helpful to understand the anatomy of the knee joint which is made of three parts.

🔵The inside of the knee called the ‘medial compartment’.

🔵The outside of the knee called the ‘lateral compartment’.

🔵The front side of the knee under the kneecap, called the ‘patellofemoral compartment’.

Image showing the three knee compartments which accommodate the prosthesis

1️⃣ A partial knee replacement replaces only the damaged part of the knee i.e. the inside (medial) or the outside (lateral) compartment

2️⃣A total knee replacement involves replacing all the compartments of the knee joint.

3️⃣ A patellofemoral joint replacement is an option when damage is confined to the area.

▶️What is the average lifespan expectancy of a knee replacement?

When you have had any type of knee replacement, you should keep it in mind that these are effective mainstay knee treatment.

Given time, all knee replacements will fail and knowing when this failure might happen is important.

Having x-rayed so many patients with total knee replacement, I only have a rough idea on how long these knee replacements last.

Usually, I do ask my patients how long they have had their knee replacement and to my surprise some of them claim to have had them for more than 10 years or more.

To determine how long knee replacement will last, I will rely on some of the medical studies that follow operated individuals for over 25 years.

Here is the most reliable and recent data I found on the subject, and they are very reassuring:

Clinical eligible case series done in over 30 articles, by Lancet 2019.

shows that approximately 82% of total knee replacement can last 25 years and 70% of unicondylar knee replacement can last 25 years.

There have been instances of knee replacements lasting longer than 25 years.

An analysis that used the UK Clinical Practice Research Datalink database published in 2017. Estimated survival of total knee replacement to be 89·7% at 20 years.

These figures are based on the follow-up of over 6490 patients who underwent knee replacement surgery for different reasons, in ten countries.

▶️What factors can influence the lifespan of a knee replacement.

It is difficult to clearly identify the factors that influence the risk of needing knee reoperation after receiving one.

The later you undergo surgery, the lower your risk of needing another operation.

This makes more sense, if you receive your knee replacement at 80 you are less likely to have a revision then someone who is 40 years old.

Here are some of the scientific literatures which could partly influence at an individual level.

According to Stone,2022

1️⃣The lifetime risk of requiring revision was 22.4% in those aged between 46 and 50 years at the time of the initial surgery.

2️⃣Decreased linearly with increasing age to 1.15% in those aged between 90 and 95 years at the time of surgery.

3️⃣You should also mind your weight because I have seen some surgeons refuse to operate on the knee unless you lose weight.

Reason being you may be at a higher risk of needing reoperation then those who are not obese.

So, the risk decreases with age.

▶️How do you know when your knee replacement is worn out?

After years of having your knee replacement you may start having sudden indications with or without injury to your knee replacement.

However, some people have had a knee replacement for over 25 years without experiencing discomfort or pain.

I am not telling you this to worry you, You may not need a replacement but just know it is inevitable sometimes.

▶️The most common symptoms of a worn-out knee implant are.

🟠Pain alone does not necessarily mean you need a replacement, but pain associated with other symptoms can be a sign of a knee worn out.

🟠Decrease in joint function.

🟠Knee instability or loosening of the joint, this occurs when the bone fails to grow around the part of the knee with the knee implant.

🟠Swelling and stiffness in the knee joint.

🟠Fractures around the replacement.

All these signs are not highly clinical to indicate a definite knee wear.

Usually, imaging tests and a doctor’s initial assessment can confirm prosthesis wear

▶️Can knee replacement be done twice?

Yes, knee replacement can be done twice. There are several reasons why your doctor will decide to redo your surgery.

🟠Some patients achieve poor results after surgery, or the implant fails or an allergy against implant materials and a revision surgery is required.

In this procedure, your doctor removes some or all the parts of the original prosthesis and replaces them with new ones.

According to some research analysis:

🟠Periprosthetic joint infection was the most common reason for revision and re-revision of knee replacement (Postler,2028)

🟠Aseptic loosening, polyethylene wear and instability.

🟠Periprosthetic fracture that can cause pain and restricted range of motion/fibrosis, extensor mechanism insufficiency

Analysis of total knee arthroplasty revision causes: Postler 2018:

▶️How many knee replacements can you have in a lifetime

Two to three revisions of total knee arthroplasties are typically acceptable for pain relief, improved function, and reduced infection risk

But this will depend on the individual care plan.

If you begin experiencing increased pain and discomfort in your prosthetic knee for several weeks, you can discuss it with your doctor or physical therapist.

We have come to the end of this article; I wish you a quick recovery:🙋 your comments are welcome.