Revision Knee Replacement: Why Knee Implants Fail and When Revision Surgery Is Needed

Most knee replacements provide years of pain relief and improved mobility. However, an artificial knee can sometimes become painful, loose, unstable or infected. When the problem cannot be corrected with non-surgical treatment or a smaller procedure, revision knee replacement may be needed.

Revision surgery means removing or replacing one or more parts of a previous knee implant. It is not simply a repeat of the first operation. The surgeon may need to identify infection, remove well-fixed components, rebuild lost bone, restore ligament balance and use specialised implants with stems or additional support. The correct plan depends on why the original knee replacement is failing.

This guide explains the common causes of knee implant failure, warning signs that need assessment, tests used before revision and what patients can expect from surgery and recovery.

What is revision knee replacement?

In a primary total knee replacement, damaged joint surfaces are replaced with metal components and a medical-grade plastic spacer. In revision knee replacement, the surgeon operates on a knee that already contains these components.

A revision may involve changing only one part when the remaining components are correctly positioned, securely fixed and compatible with the new part. In many cases, several or all components must be removed and replaced. If bone has been lost, the reconstruction may require metal augments, cones, sleeves, bone graft or longer stems that transfer load to stronger bone.

The operation is generally more complex than primary knee replacement because scar tissue changes the surgical planes and the condition of the bone and ligaments can vary. Careful diagnosis and planning are therefore central to a successful revision.

Why do knee implants fail?

1. Infection around the implant

Periprosthetic joint infection is one of the most important reasons for revision. Infection can occur soon after the original operation or appear months or years later. Bacteria may enter during surgery, through a wound problem or, less commonly, through the bloodstream from an infection elsewhere in the body.

Possible signs include increasing pain, swelling, warmth, redness, wound drainage, fever or a knee that never recovered as expected. Chronic infection can be subtle. Some patients have persistent pain and stiffness without fever or obvious redness.

Treatment depends on the timing, organism, implant stability and condition of the tissues. An early infection may sometimes be treated with surgical cleaning, exchange of removable parts and antibiotics while fixed components remain. Established infection often needs removal of the implant. A new knee may be inserted during the same operation in selected cases or during a second operation after infection treatment.

2. Aseptic loosening

Aseptic loosening means the implant has lost secure fixation without infection being the cause. The bond between implant, cement and bone may deteriorate over time. Wear particles can also trigger inflammation and bone loss around the components, a process called osteolysis.

Patients may notice pain while standing or walking, a gradual decline after a period of good function, or a sense that the knee no longer supports them normally. X-rays may show a change in component position, a widening line around the implant or areas of bone loss. Infection must still be excluded because it can mimic loosening.

3. Knee instability

A replaced knee needs balanced ligaments throughout its range of movement. If the soft tissues become stretched, damaged or incorrectly balanced, the knee may feel loose, buckle, shift or lack confidence on stairs. Instability can also follow component wear or malposition.

Physiotherapy may help when weakness is the main problem, but it cannot correct a mechanically unstable implant. The evaluation must identify whether instability occurs in extension, flexion, throughout movement or only in a specific direction. Revision components with a different degree of constraint may be needed when ligament support is inadequate.

4. Wear of the plastic spacer

The polyethylene spacer between the metal components can wear over time. Modern materials have improved, but wear still occurs in some knees, particularly with long implantation time, high loads, alignment problems or instability. Wear can lead to asymmetry, particle-related bone loss and loosening.

Replacing only the spacer is appropriate in limited situations. The surgeon must confirm that the other components are secure, correctly positioned and compatible, and that the cause of wear has been addressed.

5. Stiffness and scar tissue

Some knees develop severe stiffness from scar formation, infection, component position, pain-related guarding or another mechanical cause. Manipulation under anaesthesia or scar-tissue removal may help selected patients earlier in recovery. Revision is considered when stiffness remains disabling and testing shows a correctable implant-related reason.

Revision for unexplained stiffness is not automatically successful. The cause, preoperative range of movement and realistic recovery goals should be discussed carefully.

6. Fracture around the knee replacement

A fracture can occur in the femur, tibia or kneecap near a knee implant, often after a fall. Treatment depends on the fracture pattern, implant stability, bone quality and patient health. A stable implant may allow fracture fixation with plates or nails. A loose implant or major bone loss may require revision components that bridge the damaged area.

7. Component position, alignment or patellar problems

Implant position affects balance, kneecap tracking and the way forces pass through the knee. Malrotation, alignment problems, overhang or an incorrectly sized component can contribute to pain, stiffness or instability. The kneecap can also develop tracking problems, fracture, wear or instability. Not every abnormal-looking X-ray causes symptoms, so imaging findings must match the examination.

What symptoms suggest a knee replacement problem?

Pain after knee replacement does not always mean the implant has failed. Tendon irritation, back or hip problems, nerve pain, weakness and other conditions can produce knee-area symptoms. Revision surgery should only be offered when the cause is understood and the expected benefit outweighs the risk.

Arrange an orthopedic review if you develop:

• New or increasing pain after a period of good function
• Persistent swelling, warmth or stiffness
• Repeated buckling, shifting or a feeling of instability
• Reduced walking distance or difficulty with stairs
• A change in leg alignment
• Clicking accompanied by pain or instability
• Wound drainage, redness or fever
• Sudden pain or inability to bear weight after a fall

Urgent assessment is appropriate for wound drainage, fever with a hot swollen knee, sudden severe pain, deformity, inability to bear weight or symptoms of a blood clot such as new calf swelling or breathlessness.

How does a surgeon find out why the implant is failing?

The investigation starts with the story of the original operation and the timing of symptoms. Bring previous operative notes, implant details, discharge records, culture reports and earlier X-rays if available. Comparing images over time can reveal gradual movement or bone loss that is difficult to judge on a single film.

Examination and X-rays

The surgeon assesses walking, alignment, range of movement, ligament stability, kneecap tracking, tenderness, swelling and the condition of the skin. Weight-bearing X-rays show component position, fixation, alignment, wear, fracture and bone loss.

Blood tests and joint aspiration

When infection is possible, blood markers such as C-reactive protein and erythrocyte sedimentation rate may be requested. Abnormal or suspicious findings can lead to aspiration, in which joint fluid is collected under sterile conditions for cell count, culture and other tests. Antibiotics taken before aspiration may affect culture results, so patients should follow the treating team's instructions rather than starting antibiotics independently.

Additional imaging

CT can help assess component rotation, bone loss or fracture anatomy. Nuclear medicine scans and other tests may be used selectively, but no scan should replace clinical correlation. The goal is to establish a defensible diagnosis before planning another major operation.

Patients seeking assessment can review Dr Anshul Goel's knee replacement and revision assessment service in Rajouri Garden.

When is revision knee replacement actually needed?

Revision may be recommended when there is a clear mechanical or infectious cause that is unlikely to improve without surgery and the symptoms significantly affect function or health. Examples include a loose implant, confirmed infection, recurrent instability, major wear with bone loss, a fracture involving a loose component or severe stiffness caused by component-related problems.

Observation may be reasonable when symptoms are mild, the implant is stable and imaging shows no progressive damage. Physiotherapy, activity modification, weight management, pain treatment or treatment of a hip, spine or soft-tissue condition may help when the implant itself is not the problem.

The decision is individual. Age alone does not decide it. The surgeon considers symptom severity, diagnosis, bone quality, muscle strength, general health, infection risk, expected improvement and the demands of rehabilitation. For context on how surgeons choose between preservation and replacement in an untreated knee, read knee replacement versus knee preservation.

How is revision surgery planned?

Planning includes identifying the existing implant, predicting how much bone may be lost during removal and ensuring suitable revision components are available. Medical conditions such as diabetes, anaemia, heart or lung disease, kidney disease, obesity, malnutrition and smoking status may need optimisation before surgery.

If infection is confirmed, the surgical and antibiotic plan is coordinated around culture results and the clinical situation. If substantial bone loss or ligament damage is expected, the surgeon selects implants that provide additional fixation or stability. Blood conservation, clot prevention, pain control and rehabilitation are planned before the operation rather than after it.

What happens during revision knee replacement?

The previous incision is usually used and extended if necessary. Scar tissue is carefully released to expose the joint. Components are removed while preserving as much healthy bone as possible. The surgeon clears damaged tissue and old cement, then evaluates the remaining bone and ligaments.

Trial components help restore joint line, alignment, stability and range of movement. Bone defects may be filled or supported with graft, augments, cones or sleeves. Stemmed components can transfer load to stronger bone farther from the joint. The final implant is inserted once balance and fixation are satisfactory.

In infection surgery, the sequence may include extensive debridement and collection of multiple tissue samples. A temporary antibiotic-loaded spacer may be used between stages when a two-stage plan is chosen.

Is recovery longer than after the first knee replacement?

Often, yes. Revision surgery may involve more tissue work, bone reconstruction and a longer operation. Pain control, clot prevention, wound care and early movement remain important, but weight-bearing instructions and rehabilitation vary with the reconstruction. Some patients can bear weight early, while others need protection because of a fracture, bone graft or complex repair.

Recovery is influenced by the reason for revision, preoperative strength, infection status, bone loss and other health conditions. Improvement continues over several months, and complex revisions can take longer. The goal is usually reliable pain reduction, stability and useful function, not a knee that feels identical to a natural joint.

The primary replacement timeline in our guide to walking, stairs and daily activity after knee replacement can provide general context, but revision patients need an individual plan.

What are the risks of revision knee replacement?

Risks include infection, blood clots, stiffness, wound problems, fracture, nerve or blood-vessel injury, continued pain, instability and the possibility of another revision. Risk is generally higher than for primary knee replacement because the operation is more complex and tissues have already been operated on.

This does not mean revision should be avoided when it is needed. Untreated infection, progressive bone loss, severe instability or a loose implant can create greater problems. A clear diagnosis, medical optimisation, experienced surgical planning and rehabilitation help manage risk.

Frequently Asked Questions (FAQs)

How long should a knee replacement last?

Many knee replacements function well for 15 to 20 years or longer, but implant survival varies with age, activity, diagnosis, alignment, infection and other factors. Pain should be assessed rather than assuming an implant has reached a fixed expiry date.

Does every painful knee replacement need revision?

No. Pain can come from the hip, spine, tendons, nerves, weakness or other causes. Revision is most useful when a specific implant-related or infectious problem has been identified.

Can only the plastic spacer be replaced?

Sometimes. Isolated spacer exchange is considered only when the fixed components are secure, correctly positioned and compatible, and when the cause of wear or instability can be corrected without full revision.

Can an infected knee replacement be treated without removing it?

Selected early infections may be treated with surgical cleaning, exchange of removable parts and antibiotics. Chronic or complex infections often require implant removal. The plan depends on timing, organism, fixation and patient factors.

Is clicking after knee replacement a sign of failure?

Painless clicking can occur with artificial components and may be harmless. Clicking with pain, swelling, buckling, loss of movement or a new change deserves orthopedic assessment.

Is revision knee replacement more painful than the first surgery?

It can involve a longer recovery because the reconstruction is more complex. Modern multimodal pain control and a planned rehabilitation programme help, but individual experience varies.

Can I walk normally after revision knee replacement?

Many patients improve walking and stability, but the result depends on the reason for revision, bone and ligament condition, muscle strength and general health. Some need a walking aid during recovery or longer term.

Should I get a second opinion before revision surgery?

A second opinion can be valuable when the diagnosis is uncertain, infection testing is incomplete or a complex reconstruction is proposed. Bring all prior records and imaging so the reviewing surgeon can assess the full history.

The key takeaway

Revision knee replacement is considered when a previous implant has a clearly defined problem such as infection, loosening, instability, wear, fracture or correctable component-related stiffness. The operation is more complex than primary replacement, so the cause of pain should be established before surgery.

If a replaced knee becomes newly painful, swollen, unstable or less functional, arrange an orthopedic review. Early assessment can identify infection, fracture or progressive bone loss before the reconstruction becomes more difficult.

Sources and further reading

• AAOS OrthoInfo: Revision Total Knee Replacement
• Current Epidemiology of Revision Total Knee Arthroplasty
• Risk Factors for Re-revision Following Revision Knee Arthroplasty

Medical disclaimer: This article is for general education and does not replace examination, diagnosis or personalised surgical advice from a qualified orthopedic specialist.