Many knee replacements last beyond 20 years.[1] [2] They have no fixed expiry date, and revision surgery isn’t inevitable. Your age at surgery affects your chance of needing a revision during your lifetime.[1] The decision to proceed should balance that possibility against the pain and loss of function you are living with now.
At a glance
- Many total knee replacements remain unrevised beyond 20 years, but there is no fixed expiry date.
- The 2025 Australian registry estimates that about 92 in 100 total knee replacements for osteoarthritis remain unrevised at 20 years.
- Younger patients have a greater lifetime chance of revision.
- New pain, swelling, stiffness or instability should be assessed. These symptoms do not automatically mean revision is needed.
What is the average lifespan of a knee replacement?
An average lifespan is difficult to pin down because many implants are still in place when follow-up ends. Registry data instead tell us how many have needed revision by a particular time.[1] [2]
The 2025 Australian Orthopaedic Association National Joint Replacement Registry estimates that about 92 in 100 total knee replacements for osteoarthritis remain unrevised at 20 years.[1] A review published in The Lancet in 2019 estimated that about 82 in 100 remained unrevised at 25 years.[2]
These figures come from different populations and implant designs. They show that many replacements last well beyond 20 years, but they don’t guarantee how long your own knee replacement will last.
What do the registry results show for the Triathlon CR?
The Stryker Triathlon CR is a well-established prosthesis and one of the most commonly used knee implants in Australia.[1] Dr Vishal Pai uses it with Mako robotic assistance.
In the 2025 registry report, estimated revision rates for the Triathlon CR/Triathlon combination at 15 years were 4.5% with cemented fixation, 5.4% with cementless fixation and 4.5% with hybrid fixation. Roughly 95 in 100 remained unrevised.[1]
These are registry implant results, not evidence that robotic assistance improves knee replacement implant longevity. These tables do not provide a 20-year estimate for this combination.[1]
Does your age affect knee replacement lifespan?
Younger patients have a greater chance of needing revision during their lifetime.[1] This deserves consideration before the first operation.
Joint replacement is generally considered when pain and restricted function substantially affect daily life despite suitable nonsurgical treatment. Exercise, weight management where relevant and pain relief remain options. Age helps shape the discussion, but there is no birthday you must reach before surgery becomes appropriate.
Do knee replacements wear out?
The polyethylene plastic insert can wear over time. Tiny wear particles can trigger an inflammatory reaction that removes bone around the implant. This process, called osteolysis, can weaken its attachment and cause loosening.[7]
Wear is one reason for revision. In the Australian registry figures discussed here, infection is the most commonly recorded reason, followed by loosening. Loosening can also occur without wear-related osteolysis.[1]
What happens when a knee replacement wears out?
If the metal components have loosened and bone has been lost, replacing the plastic insert may not be enough. The components may need to be removed, and a revision knee replacement may be used to rebuild the joint. Longer stems extend into the thighbone or shinbone for support; additional implants or bone graft may fill areas of missing bone.[7]
A liner exchange is suitable in selected cases. Revision can improve symptoms, but it is more complex than the first replacement, and recovery and results can be less predictable.[6] [7]
What are the signs a knee replacement may need revision?
Increasing pain when walking, or a feeling that your knee gives way, should prompt an assessment. Persistent swelling or stiffness can also occur.[7]
These symptoms do not automatically mean you need revision. An examination and X-rays help identify the cause before considering treatment.[7]
How should you think about knee replacement longevity?
Many total knee replacements remain unrevised for more than 20 years.[1] [2] Choosing the timing of your first operation means weighing current symptoms against future revision risk. New pain or instability after having a knee replacement deserves assessment and a diagnosis before further surgery.[7]
References
Show all 7 referencesHide references
- Australian Orthopaedic Association National Joint Replacement Registry (2025). Hip, Knee and Shoulder Arthroplasty: Annual Report, tables KT2 and KT9–15; and Patient Reported Outcome Measures Supplementary Report.
- Evans JT et al. (2019). How long does a knee replacement last? A systematic review and meta-analysis of case series and national registry reports with more than 15 years of follow-up. The Lancet.
- Wilson HA et al. (2019). Patient relevant outcomes of unicompartmental versus total knee replacement: systematic review and meta-analysis. BMJ.
- Budin M et al. (2026; published online 2025). Periprosthetic joint infection risk is comparable between unicompartmental knee arthroplasty to total knee arthroplasty conversion and primary total knee arthroplasty: A systematic review and meta-analysis. Knee Surgery, Sports Traumatology, Arthroscopy.
- Mortazavi SMJ et al. (2010). Revision total knee arthroplasty infection: incidence and predictors. Clinical Orthopaedics and Related Research.
- Sabah SA et al. (2023). Patient-Relevant Outcomes Following First Revision Total Knee Arthroplasty, by Diagnosis. The Journal of Bone and Joint Surgery.
- American Academy of Orthopaedic Surgeons. Revision Total Knee Replacement. OrthoInfo.
Frequently asked questions
Is a partial knee replacement expected to last as long as a total knee replacement?
Partial knee replacement preserves more native bone and usually the cruciate ligaments, and can offer a quicker early recovery; some studies also report better knee movement.[3] Its long-term revision rate is higher, with the 2019 review estimating about 70% remaining unrevised at 25 years, compared with 82% for total knees.[2] If conversion to a total knee replacement becomes necessary, standard primary components may be suitable when bone loss is limited, but stems or augments can be needed and the operation is not always straightforward.[4]
Does reaching 20 years mean your knee replacement should be changed?
No. An implant does not need replacement simply because it reaches 20 years. Symptoms, examination and imaging guide decisions about further treatment.[7]
Can an unrevised knee replacement still be painful?
Yes. The longevity figures quoted here measure whether a knee replacement has needed revision. An implant can remain in place while you still have pain or difficulty with everyday activities, so a low revision rate does not by itself establish good knee function.[1] The Australian registry also collects patient-reported pain and function through its separate PROMs programme.[1]
What are the risks of revision knee replacement?
Revision of a total knee replacement carries a higher infection risk than a first replacement, as well as risks such as blood clots and persistent pain or stiffness.[5] [7] Before considering revision, there should be an established diagnosis that surgery can address, such as loosening, instability or infection.[6] [7] Revision for pain without an identified cause has less predictable benefits, so pain alone is not a sufficient reason to replace the implants.[6] [7]
What does implant longevity mean for your knee?
Dr Pai assesses knee arthritis and issues related to knee replacements. If you would like to discuss how this applies to your knee, you can arrange a consultation.
Written by Dr Vishal Pai
Vishal is an experienced knee surgeon based in Bayside, Melbourne. He consults at Sandringham Orthopaedic Specialists and operates at The Avenue Hospital and Calvary Holmesglen Private Hospital. His practice focuses on sports knee surgery, including ACL reconstruction and meniscal repair, as well as robotic knee replacement.