Revision Knee Replacement: When a First Replacement Needs Redoing

For most people, a total knee replacement is a highly successful operation that provides many years of pain relief and improved function. It allows a return to the daily activities that knee arthritis had made difficult or impossible. However, like any mechanical implant, a knee replacement can eventually wear out or develop problems. When this happens, a second operation, known as a revision knee replacement, may be needed. If you have a knee replacement and are beginning to experience new pain, swelling, or instability, it is understandable to be concerned. This article explains the common knee replacement complications that can lead to revision surgery, how a surgeon investigates these issues, and why a revision procedure is different from a first-time replacement.

What Does It Mean for a Knee Replacement to 'Fail'?

The term 'failure' can sound alarming, but it rarely means a sudden collapse of the knee. Instead, it usually describes a gradual process where the implant is no longer functioning as it should. A successful knee replacement is one that is stable, allows for a good range of movement, and is free from significant pain. When one or more of these conditions are no longer met, the replacement may be considered to be failing. It is important to remember that revision surgery is the exception, not the rule. The vast majority of knee replacements perform well for a very long time. Revision is a solution for a specific set of recognised problems that can develop over time.

Common Reasons for Knee Replacement Complications and Revision

A surgeon will only recommend revision surgery after a thorough investigation identifies a clear cause for your symptoms. Several well-understood issues can lead to this point.

Aseptic Loosening: Over many years, the bond between the implant and the bone can slowly weaken. This is the most common reason for revision surgery long-term. The implant becomes slightly loose, which can cause pain as it moves against the bone. This is not caused by infection, which is why it is called 'aseptic' (meaning sterile) loosening.

Wear of the Bearing: The metal components of a knee replacement are separated by a highly durable plastic spacer (polyethylene). Over time, just like the tread on a tyre, this plastic surface can wear thin. The tiny wear particles can trigger an inflammatory response from the body, which can also contribute to the loosening of the implant.

Infection: A deep infection around the implant is a serious complication. It can occur soon after the initial surgery or even many years later. An infected knee replacement typically becomes painful, swollen, and warm. Treating it usually requires at least one, and often two, separate operations to clear the infection and implant a new prosthesis.

Instability: If the knee feels wobbly, unsteady, or gives way, it is described as unstable. This can happen if the soft-tissue ligaments surrounding the knee stretch out over time, or if the components were not perfectly balanced during the initial surgery. It can make walking on uneven ground or stairs feel particularly unsafe.

Stiffness: While some stiffness is normal during recovery, most patients achieve a good functional range of motion. In some cases, excessive scar tissue can build up inside the knee (a condition called arthrofibrosis), severely limiting movement. If extensive physiotherapy fails to improve motion, a revision may be considered to release the scar tissue and restore movement.

Periprosthetic Fracture: A significant fall or injury can cause the bone around the knee replacement to break. These fractures (known as periprosthetic fractures) can sometimes be fixed with plates and screws, but if the fracture makes the implant unstable, a revision surgery is often necessary to fix the bone and replace the original components.

The Key Sign: A Change After a Period of Good Function

It is vital to distinguish between the normal process of recovery and the signs of a late problem. For the first year after a knee replacement, it is common to have some residual swelling, warmth, and discomfort as your body heals. However, the pattern that suggests a problem is different. The key sign is a change in a knee that has been functioning well for a number of years. If you had a long period of good, pain-free function and now begin to experience new or worsening pain, new swelling or warmth, a feeling of instability, or a change in your ability to walk, this warrants a review with an orthopaedic surgeon. It is important to have these signs evaluated.

How a Surgeon Investigates a Problematic Knee Replacement

When you see a surgeon for a problematic knee replacement, they will follow a structured process to find the cause of the issue. This work-up is essential to planning the right treatment.

First, the surgeon will take a detailed history of your original surgery, your recovery, and the specific symptoms you are now experiencing. They will perform a careful physical examination of your knee, assessing your range of motion, stability, and locating any areas of tenderness.

X-rays are fundamental. The surgeon will compare current X-rays with films taken in previous years. This comparison is crucial for detecting subtle changes over time, such as the shifting of an implant, bone loss, or thinning of the plastic spacer. In some cases, other imaging like a CT scan might be ordered to get a more detailed view of the bone and implant position.

Blood tests that measure markers of inflammation, such as the ESR and CRP, are usually performed. While these tests cannot prove there is an infection, elevated levels can raise suspicion and point towards the need for further investigation.

If infection is suspected, the next step is often to take a sample of fluid from within the knee joint. This procedure, called a joint aspiration, involves carefully cleaning the skin and then passing a fine needle into the knee to draw out a small amount of fluid. The fluid is sent to a laboratory to be tested for bacteria. This is one of the most reliable ways to confirm or rule out a deep infection.

Signs That May Warrant Urgent Medical Attention

While most issues with a knee replacement develop gradually, certain signs are generally regarded as reasons for urgent medical evaluation rather than a scheduled appointment. These include the sudden onset of severe pain in the knee, especially if you cannot put any weight on your leg. Significant and rapid swelling with redness and heat, particularly if accompanied by a fever or feeling generally unwell, can be a sign of an acute infection. Any obvious deformity of the leg or knee after a fall or injury suggests a possible fracture. These situations are typically considered reasons for prompt assessment at a hospital emergency department.

Why Revision Knee Surgery Is More Complex

Revision knee replacement is a more challenging and extensive procedure than a primary (first-time) knee replacement for several reasons. The surgeon is not starting with a clean slate.

First, the old components must be removed. These implants were designed to stay fixed to the bone, often with bone cement. Removing them requires special instruments and techniques to detach them without damaging the surrounding bone. This part of the procedure can be time-consuming and technically demanding.

The process of implant failure and its removal can result in bone loss. This means the surgeon has less healthy bone stock to fix the new revision implant to. To overcome this, revision implants are often designed differently. They may have longer stems that extend further into the femur (thigh bone) and tibia (shin bone) for added stability, or they may use metal augments to fill in areas of lost bone.

The presence of scar tissue from the first surgery makes the exposure and dissection more difficult. The recovery can also be affected, as the soft tissues have been disturbed more than once. Because of these factors, revision surgery typically takes longer in the operating theatre and can involve a greater blood loss. The post-operative care and rehabilitation are just as important, but the timeline for recovery may be longer than after a primary replacement.

Choosing a Surgeon for Your Revision Procedure

Because it is a more complex operation, the choice of surgeon for a revision knee replacement is particularly important. This is a sub-specialist field within orthopaedics. When considering a surgeon, it is fair and reasonable to ask about their experience with revision procedures. You might ask if they perform revision knee surgery regularly, what their general approach is to investigating knee replacement complications, and at which hospital the surgery would be performed. The chosen hospital must have the specialised revision implants and instruments required. A successful outcome depends on a correct diagnosis, a skilled surgical team, and a clear plan that has been discussed with you. The decision to proceed must be a shared one, made only after you feel you have all the information you need.

If you are experiencing problems with your knee replacement and wish to understand your options, a consultation is the necessary next step. Dr Farooq Azam Khan is a consultant orthopaedic and joint replacement surgeon in Lahore who can assess your specific situation and discuss a potential way forward.