Signs Your Knee Replacement Is Failing: When to See Your Surgeon
Key takeaways
- The main warning signs are new or worsening pain, swelling, instability, stiffness, clicking, or signs of infection.
- A deep infection around the implant affects about 1 to 2 in 100 people and needs urgent assessment.
- Most knee replacements last 15 to 20 or more years, and around 90 to 95% are still in place at 10 years, so failure is the exception.
- About 1 in 5 people have some lasting stiffness or ache, which is not the same as the implant failing.
- If you have a hot, swollen, increasingly painful knee or a fever, seek medical help the same day.
By Margaret Doyle | Medically reviewed by Mr Paul Henderson, FRCS (Tr&Orth)
Updated May 22, 2026 · 3 min read
The main signs a knee replacement is failing are new or worsening pain, increasing swelling, a feeling of instability, growing stiffness, clicking with other symptoms, or signs of infection. Most of these are uncommon, because a knee replacement typically lasts 15 to 20 or more years and around 90 to 95% are still in place at 10 years1. The point of knowing the signs is to act early, when problems are easiest to manage.
After my own surgery I worried about every twinge, and I could not always tell a normal recovery ache from something that mattered. This guide, checked by a consultant orthopaedic surgeon, sets out what is normal, what is not, and when to seek help, including urgently. For the procedure and recovery context, see our knee replacement surgery guide.
New or worsening pain
Pain that is new, steadily worsening, present at rest or at night, or clearly different from your settled normal is the most important warning sign. Some background ache is expected, but a clear change is not. Persistent, worsening pain is one of the main reasons a knee is investigated for revision2.
The honest reality is that about 1 in 5 people feel the knee is never quite normal, with some stiffness or weather-change ache that comes and goes3. That low-level ache is not failure. What concerns surgeons is pain that builds over weeks, hurts on weight-bearing, or disturbs sleep. If your pain is changing for the worse, get it assessed.
Swelling, instability, and the knee giving way
Increasing swelling, a sense that the knee is loose, or episodes of it giving way can point to loosening or a problem with the implant. Over many years the implant can loosen from the bone, which is one of the more common reasons a replacement eventually fails2.
Some swelling is normal in recovery and can take months to settle4. The concern is swelling that returns or worsens after the knee had settled, especially with pain or a feeling of instability on stairs or uneven ground. If your knee feels untrustworthy under you in a way it did not before, report it.
Stiffness and loss of movement
A clear loss of the bend you had regained, or a knee that becomes progressively stiffer after settling, is worth checking. Regaining and keeping the bend is the key early goal of recovery, and physiotherapy continues for months5. Losing that ground later is different from the normal early stiffness.
Early stiffness can sometimes need a manipulation under anaesthetic to free up movement, a recognised early complication. Later, a knee that tightens up after being mobile may signal scar tissue, loosening, or another issue. Tell your surgeon if your range of movement is going backwards rather than holding or improving.
Signs of infection: act the same day
A knee that becomes hot, red, increasingly swollen and painful, leaks fluid, or comes with a fever may be infected, and this needs urgent assessment. A deep infection around the implant affects about 1 to 2 in 100 people, is serious, and can need further surgery3.
Seek medical help the same day if you have:
- A hot, red, swollen knee that is rapidly more painful.
- Fluid or pus leaking from the wound.
- A fever or feeling generally unwell with knee symptoms.
Infection can occur early after surgery or, less often, years later if bacteria reach the implant through the bloodstream. The long-term protective habits are covered in caring for your new knee long-term. Do not wait for a routine appointment if you have these signs.
What happens if the implant is failing
If assessment confirms the implant has worn, loosened, become infected, or is unstable, your surgeon may recommend a revision knee replacement, where some or all of the implant is replaced. Revision is more complex than the first operation but can relieve pain and restore function2.
Not every problem needs surgery, which is exactly why early assessment matters: the right step depends on the cause. Catching a problem while it is small usually means a simpler solution. For how often the joint should be reviewed and the habits that protect it, see caring for your new knee long-term.
References
- How long does a knee replacement last?, National Joint Registry. ↩
- Revision Total Knee Replacement (OrthoInfo), American Academy of Orthopaedic Surgeons. ↩
- Total Knee Replacement (OrthoInfo), American Academy of Orthopaedic Surgeons. ↩
- Knee replacement: Recovery, NHS. ↩
- Knee replacement surgery, Versus Arthritis. ↩
Common questions
What are the first signs of a failing knee replacement?
The earliest signs are usually new or worsening pain that is different from your normal recovery aches, increasing swelling, a feeling that the knee is loose or unstable, and growing stiffness. Clicking or a sense the knee may give way can also occur. Because most replacements last well, these signs are uncommon, but any clear, persistent change from your settled normal deserves a check by your surgeon.
How do I know if my knee replacement is infected?
Signs of infection include a knee that becomes hot, red, increasingly swollen and painful, fluid leaking from the wound, feeling generally unwell, or a fever. A deep infection around the implant affects about 1 to 2 in 100 people and is serious, sometimes needing further surgery. If you have these signs, especially a fever with a hot, painful knee, seek medical help the same day rather than waiting.
Is it normal to have pain years after a knee replacement?
Some people have a mild, occasional ache, including a weather-change sensation, for the long term: about 1 in 5 feel the knee is never quite normal. That low-level background ache is not the same as a failing implant. What concerns surgeons is new pain, pain that steadily worsens, pain at rest or at night, or pain with swelling and instability. A clear change from your settled normal should always be assessed.
Can a knee replacement come loose?
Yes. Over many years the implant can loosen from the bone, which is one of the more common reasons a knee replacement eventually fails and may need a revision. Loosening tends to cause pain on weight-bearing and a sense of instability, and shows on an X-ray. It is uncommon in the first decade: around 90 to 95% of replacements are still in place at 10 years. Report new pain or instability so it can be checked.
What happens if my knee replacement fails?
If assessment shows the implant has worn, loosened, become infected, or is unstable, your surgeon may recommend a revision knee replacement, where some or all of the implant is replaced. Revision surgery is more complex than the first operation but can relieve pain and restore function. The right step depends on the cause, which is why early assessment matters: not every problem needs surgery, and some are managed in other ways.
When should I worry about clicking in my knee replacement?
A faint, painless click is common with a knee replacement and is usually just the metal and plastic components moving, not a problem. Worry if clicking appears alongside pain, swelling, instability, or a feeling the knee may give way, or if a new, loud, or catching click develops after a settled period. Clicking on its own, with no other symptoms, rarely signals failure, but report any new combination of symptoms.
Written by Margaret Doyle. Medically reviewed by Mr Paul Henderson, FRCS (Tr&Orth).
Our guides are written from personal experience and reviewed by a qualified clinician for accuracy. Read our editorial policy.