How Long Does a Knee Replacement Last? The 25-Year Answer & The Critical Factor Your Surgeon May Not Mention
Published on November 4, 2025
"How long will my new knee last?" It's one of the most common and important questions we hear in Physiotherapy clinics. Until recently, the answer was based on limited data. Now, a landmark systematic review and meta-analysis published in *The Lancet* provides one of the most comprehensive answers to date, analysing data from over 300,000 knee replacements.
The Bottom Line: The research found that 82% of total knee replacements (TKRs) and 70% of partial knee replacements (UKRs) last for 25 years. However, the longevity of the implant itself may only be part of the story for long-term success.
The Landmark Research: Methods and Key Findings
The study, led by Evans et al., synthesised data from two primary sources: published case series and national joint replacement registries. By pooling results from sources like the Australian and Finnish registries, they achieved a much larger and more reliable sample size than any single study could provide.
The primary outcome was "all-cause revision" – meaning any surgery to remove or replace part of the knee implant for any reason, including infection, loosening, instability, or persistent pain.
25-Year Survival Rates at a Glance
| Type of Knee Replacement | 15-Year Survival | 20-Year Survival | 25-Year Survival |
|---|---|---|---|
| Total Knee Replacement (TKR) | 93.0% | 90.1% | 82.3% |
| Partial Knee Replacement (UKR) | 76.5% | 71.6% | 69.8% |
A crucial finding was that data from national registries is more accurate than data from individual surgeon case series. Case series tended to report overly optimistic survival rates, potentially due to publication bias, where only the best results are published.
Beyond the Implant: A Physiotherapist's Critical Perspective on Long-Term Success
While this data is incredibly valuable for setting patient expectations, it only tells half the story. As a Physiotherapist, I see a critical factor that often gets overlooked: a knee replacement is a brilliant solution for a worn-out knee, but it does not automatically fix the underlying biomechanical problems that caused the joint to wear down in the first place.
Think of your knee as the middle of a chain. It is powerfully influenced by what happens at the joint above (the hip and lower back) and the joint below (the ankle).
- Weak Hip Muscles: If your gluteal muscles are weak, your thigh bone can fall into adduction and internal rotation during walking. This creates a constant, abnormal stress on the inner side of your knee replacement, accelerating wear.
- Poor Lower Back Mobility: Stiffness in the thoracic and lumbar areas can disrupt your entire lower leg function, forcing the hip and knee to compensate with sub-optimal movements.
- Restricted Hip Joint Mobility: A stiff hip will transfer excessive rotational forces down to the knee, preventing it from moving as the engineers intended.
If these root causes—low back dysfunction, hip joint restrictions, and poor hip strength—are not addressed before and after surgery, they may still be present long after the new knee or hip is in. These persistent dysfunctional patterns may compromise how the implant is loaded, increasing the potential for wear, and ultimately shorten the lifespan of an otherwise perfectly installed knee or hip replacement.
Understanding the Study's Limitations
While this is a wide-reaching study, it's important to understand its constraints, which is a hallmark of a balanced scientific interpretation:
- Aggregated Data: The results are a population-level average. They are not adjusted for individual patient factors like age, weight, activity level, or specific surgical technique, which can all influence longevity.
- Geographical Focus: The long-term data (20 and 25 years) for TKRs and all data for UKRs came exclusively from the Finnish registry. While the sample size is huge, practices and outcomes can vary between countries.
- "Revision" as the Endpoint: The study defines "failure" as a revision surgery. It does not account for patients who have a painful or poorly functioning knee but do not undergo a second operation.
Maximising the Lifespan of Your Knee Replacement: A Proactive Guide
To ensure you are in the 82% group 25 years from now, a proactive approach is essential. This goes beyond just the surgery itself.
- Pre-Habilitation ("Pre-Hab"): Work with a Physiotherapist *before* your surgery. The goal is to correct the underlying biomechanical issues—strengthen your hips, improve your trunk mobility and strength, and restore range of motion to your ankles and hips. A stronger, more flexible, and more biomechanically optimal lower half going into surgery tends to lead to a much better recovery.
- Commit to Post-Op Rehabilitation: Post-surgery physiotherapy is non-negotiable. It's not just about bending and straightening the new joint; it's about retraining your entire leg chain to work together efficiently and protect the new joint.
- Maintain a Healthy Weight: Every extra pound multiplies the force going through your knee implant during walking and other activities.
- Choose Smart Activities: Opting for lower-impact exercises like swimming, cycling, and walking over high-impact activities like running or jumping may help minimise wear and tear.
The Final Word
The Lancet study provides excellent news: modern knee replacements are durable and designed to last for decades. However, the long-term success of your new joint is a partnership between the surgeon's skill, the quality of the implant, and your commitment to addressing the whole-body mechanics that support it.
By understanding that the implant is a tool and not a cure-all, you can take proactive steps to ensure it serves you well for the rest of your life.
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