The unicompartmental knee arthroplasty, often a preferred solution for limited cartilage wear in the knee, offers many patients improved quality of life and mobility. However, like all implants, the unicompartmental knee arthroplasty has its limitations. If it fails, a revision to a total knee arthroplasty (TKA) is required. In this blog, you will learn when and why such a prosthesis revision is necessary, what options are available, and why modern surgical methods make these interventions safe and effective.

A common reason for revision of a unicompartmental knee arthroplasty is the progression of osteoarthritis to other parts of the knee joint that were still healthy during the original surgery. Fortunately, the revision from a unicompartmental knee arthroplasty to a total knee replacement is, in most cases, a well-planned and complication-free procedure.

In this comprehensive blog, we take a detailed look at the background of a prosthesis replacement. We clarify the most common causes and modern treatment approaches. Whether you are directly affected or simply want to inform yourself – here you will find all the answers about switching to a TKR.

Reasons for revising a unicompartmental knee arthroplasty to a total knee arthroplasty

Replacing a unicompartmental prosthesis with a total knee replacement (TKR) becomes necessary when the original prosthesis no longer functions properly. The main causes can be divided into four categories:

1. Progressive osteoarthritis:
   Originally, the sled prosthesis was designed to limit the damage to a limited area of the knee joint. However, in many cases, cartilage loss progresses over time and affects other joint sections, especially the cartilage behind the kneecap (retropatellar). In such cases, the partial prosthesis is no longer sufficient, and a TKR becomes necessary.
2. Loosening and wear:
   Although modern partial knee replacements are durable, they can loosen or wear out over the years. Reasons for this are often overuse or age-related changes in bone density, which affect the stability of the prosthesis.
3. Infections:
   A periprosthetic infection is one of the most feared complications after knee surgery. Although rare, it may necessitate the removal of the partial knee prosthesis and replacement with a total knee replacement.
4. Instability:
   If the knee does not feel stable enough after implantation or shows repeated failures, this is a clear signal for a necessary revision. A total knee replacement (TKR) provides more comprehensive support and higher stability in these cases.

Signs of failure of a partial knee replacement

A sled prosthesis initially allows for a high degree of mobility and functionality, but problems can arise over the years. There are clear signs that the prosthesis is no longer performing its task optimally.

• Increasing pain: If pain occurs that persists even at rest or during light activities, this is a warning sign. Particularly stressful are dull, persistent pain in the knee or stabbing pain when stressed.
• Limitations in everyday life: Affected individuals often report difficulties when walking, climbing stairs, or performing other everyday movements. Swelling in the knee can also indicate a malfunction.
• Knee instability: A feeling as if the knee is giving way or is wobbly indicates mechanical problems with the prosthesis. This is often associated with reduced confidence in the stability of the leg.
• Radiological Changes: Imaging techniques like X-ray or MRI often show early signs of loosening, wear, or misalignment of the prosthesis.

Early medical clarification of these symptoms can prevent the complaints from worsening and a more comprehensive revision from becoming necessary.

Diagnosis before prosthesis revision

Before a revision from a unicompartmental knee arthroplasty to a total knee replacement is performed, a precise diagnosis is required. Doctors use a combination of medical history, clinical examination, and state-of-the-art diagnostic procedures to determine the need for revision.

1. Medical History: Patients are specifically asked about their symptoms, such as the type and intensity of pain, time of occurrence, and limitations in daily life.
2. Clinical examination: Orthopedic surgeons check the mobility, stability, and alignment of the knee. Swelling, redness, or warmth in the area of the prosthesis may indicate inflammation.
3. Imaging:

• X-ray: Shows mechanical changes such as loosening or malpositioning.
• MRI: Provides detailed images of soft tissues and helps identify inflammation or progressive osteoarthritis.
• Scintigraphy: Used to detect infections or bone remodeling activities.

1. Laboratory tests: Blood tests for infection markers such as CRP or leukocyte count are essential to rule out infection.

This comprehensive diagnosis lays the foundation for planning the revision and helps tailor the appropriate therapy to the individual patient.

Prosthesis replacement: From partial knee replacement to total knee replacement

A change from a partial knee replacement to a total knee replacement (TKR) is often the next step when the partial prosthesis no longer fulfills its task.

• Procedure of the replacement: The procedure begins with the removal of the sled prosthesis. This is done with great care to preserve the surrounding bone and soft tissues. The affected joint area is prepared, and the new TKR is precisely fitted. Modern implants allow for optimal adaptation to the patient's individual anatomy.
• Challenges: The biggest challenges lie in the precision of bone preservation and the restoration of the biomechanics of the knee. Experienced surgeons can, however, master these hurdles with the latest technology.
• Minimally invasive approaches: By using gentle surgical techniques, the strain on the body is reduced, contributing to a faster recovery.

Thanks to advanced techniques, this procedure is usually well-planned and associated with high success rates.

Follow-up care and rehabilitation after prosthesis replacement

Aftercare is crucial for successful recovery and long-term stable knee function.

1. Physiotherapy: Patients start exercising under guidance to mobilize and strengthen the muscles just days after the surgery. The goal is to restore the natural mobility and function of the knee.
2. Weight relief: For several weeks, the use of crutches may be necessary to relieve the operated knee and allow the implant time to fully integrate.
3. Daily Assistance: Patients are instructed on how to safely manage daily situations like climbing stairs or lifting. Assistive tools like occupational therapy can also be supportive.
4. Regular check-ups: Follow-up appointments monitor the healing process. X-rays help to check the position and function of the implant.

A structured rehabilitation program significantly contributes to minimizing complications and quickly restoring quality of life.

Why the change is often possible without problems

Thanks to gentle surgical techniques and the experience of knee specialists, the replacement of a partial knee prosthesis with a total knee replacement usually proceeds smoothly.

• Bone preservation: During the implantation of a partial knee replacement, less bone is removed, which is advantageous in case of a later revision.
• Modern Implants: Total Knee Replacements (TKR) offer individual adaptation options, allowing them to fit seamlessly into the existing anatomy.

These factors make prosthesis replacement a safe and effective procedure today with excellent long-term results.

Technical challenges when switching from a sled prosthesis to a total knee replacement

A revision from unicompartmental knee arthroplasty to total knee arthroplasty is a complex procedure, which, however, is safely feasible thanks to modern surgical methods and experienced surgeons. Some challenges are:

• Removal of the old prosthesis: Gentle removal of the sled prosthesis without further damage to the bone is crucial.
• Reconstruction of anatomy: The surgeon must ensure that the new total knee replacement is precisely positioned and the natural joint geometry is restored as well as possible.
• Soft tissue damage: The surgery potentially involves greater soft tissue stress, especially if ligaments or structures are weakened by the previous intervention.
• Precision of Implantation: Malpositions must be strictly avoided as they can lead to premature wear or new complaints.

Modern surgical techniques for replacing a unicompartmental knee prosthesis with a total knee endoprosthesis (Knie-TEP)

Minimally invasive surgery has made significant progress in recent years, which has also significantly improved the transition from unicompartmental knee replacement to total knee replacement.

• Navigation and robotics: Modern techniques ensure maximum precision in positioning the new prosthesis, improving long-term results and reducing the risk of complications.
• Bone Preservation: Surgeons use minimally invasive approaches to preserve healthy bone substance as much as possible.
• Gentle Soft Tissue Surgery: Reducing soft tissue damage reduces postoperative pain and promotes faster recovery.
• Optimized access: Optimized accesses minimize scarring and reduce the risk of infections.

These advances make the procedure significantly less stressful for patients today and increase the chances of success.

The role of rehabilitation after prosthesis replacement

After switching from unicompartmental knee arthroplasty to total knee arthroplasty, rehabilitation is a crucial factor for the long-term success of the surgery. Rehabilitation aims to restore strength, stability, and mobility in the operated knee and facilitate a return to daily life.

• Early Mobilization: As early as the first or second day after surgery, patients begin with gentle exercises under the guidance of a physiotherapist. This promotes blood circulation, reduces swelling, and supports healing.
• Targeted Strengthening: Exercises to strengthen the thigh muscles and surrounding structures help to optimally stabilize the new joint.
• Gait analysis: Physiotherapists work with patients to restore a consistent gait pattern to avoid incorrect loading.
• Relevant Daily Exercises: Climbing stairs or walking on uneven terrain is also specifically trained to increase safety in daily life.
• Long-term physiotherapy: Even months after surgery, patients benefit from regular exercises to ensure full mobility and function of the joint.

An individualized rehabilitation program tailored to the patient's needs and goals maximizes healing chances and quality of life.

Summary: Switching from unicompartmental knee arthroplasty to total knee arthroplasty

Replacing a unicompartmental knee prosthesis with a total knee endoprosthesis (Knie-TEP) is often a necessary step when complications such as arthrosis progression or loosening occur. Thanks to modern surgical techniques and high-quality implants, this procedure is highly successful in most cases.

The total knee replacement represents a comprehensive solution that not only reduces pain but also restores the stability and function of the knee joint in the long term. Supported by targeted rehabilitation and follow-up care, patients can usually lead an active, pain-free life again in most cases.

Switching from a unicompartmental prosthesis to a TKR may seem intimidating at first glance, but it is a routine procedure that is performed extremely safely in specialized centers and by experienced knee surgeons. Thanks to modern surgical techniques, high-quality implants, and optimized rehabilitation programs, patients today have a very good chance of permanently regaining their mobility and quality of life.

Specialized centers for knee arthroplasty have a comprehensive understanding of the individual needs and challenges that come with prosthesis replacement. They not only offer excellent surgical expertise but also patient-oriented care that provides security before, during, and after the operation.

Conclusion: Those who entrust themselves to a specialized expert early on benefit from precise diagnoses, tailored treatment strategies, and the best chances for a complication-free recovery.