A total knee replacement (TKR) is recommended when conservative measures (physiotherapy, medication, injections, weight loss, assistive devices) no longer provide lasting pain relief and functional improvement, and quality of life is severely impaired. The surgery aims to eliminate pain, correct misalignments, and restore mobility. This applies to both total knee replacement (TKR) and partial replacements (e.g., unicompartmental knee replacement) – the choice depends on the extent and location of joint degeneration as well as patient-specific factors.

Why the correct indication is so important for a knee replacement

the appropriate indication —that is, deciding who will benefit from which procedure—is the most important factor for a good outcome. Not every person with knee osteoarthritis automatically needs a total knee replacement (TKR); in early or unilateral cases, a unicompartmental knee arthroplasty (UKA) or a surface replacement may be more suitable. Equally important is a thorough assessment of comorbidities, leg alignment, ligament instability, and the condition of the patellofemoral joint surface, because incorrect selection leads to dissatisfied patients, premature revisions, or persistent symptoms. Therefore, the surgeon's experience, precise diagnostics (X-ray, possibly MRI, clinical examination), and individualized patient counseling are crucial.

Types of knee replacements — briefly explained

1. Total knee replacement, complete artificial knee joint (knee arthroplasty)

Total TKR) replaces the joint surfaces of the thighbone (femur), shinbone (tibia), and usually also the back surface of the kneecap (patella) with metal-plastic components. It is the standard treatment for advanced, multi-compartmental osteoarthritis, deformities, or when multiple joint components are affected. Modern implants can be very durable and reliably eliminate pain. OrthoInfo+1

2. Partial joint replacement

A partial knee replacement replaces only one previously isolated affected compartment (medial or lateral). Advantages: bone-sparing, usually faster recovery, more natural knee kinematics with appropriate patient selection. Disadvantages: not suitable for extensive multi-compartment osteoarthritis, advanced ligament or axial problems, or inflammatory arthritis. Good long-term results have been documented with careful patient selection.

3. Patellofemoral Prosthesis (PFJ/PFA)

Patellofemoral arthroplasty replaces only the joint between the kneecap and femur. It is an option for isolated patellofemoral osteoarthritis (PFJ osteoarthritis), offers a less invasive replacement, and can largely preserve the original kinematics. The results are variable—but often very good with careful patient selection.

Preliminary examinations: how is it decided which implant is suitable?

The following must be done before the operation:

• detailed medical history (pain profile, functional limitations, expectations),
• clinical examination (stability, range of motion, leg axis),
• X-rays taken in defined planes (weight-bearing AP, lateral, oblique views), often supplemented by full-leg X-rays for axis determination,
• MRI may be used to assess menisci, cartilage and soft tissues, especially in young patients or in cases of unclear findings.

Together with the patient, the best form of therapy (conservative vs. UKA vs. TEP vs. PFJ) is then decided. This phase is crucial for success.

Knee replacement surgery: Procedure in brief

1. Anesthesia: Regional (spinal/epidural) and/or general.
2. Access and preparation: Bone and cartilage are removed according to the chosen implant.
3. Component fitting: Metal components on the femur and tibia, with a polyethylene gliding surface in between. A patellar component may be included in cases of patellar replacement.
4. Examination of leg axis, soft tissue balance and range of motion.
5. Closure and wound care.

The operation typically lasts between 60 and 120 minutes, depending on the complexity and type of prosthesis. Modern techniques (minimally invasive, computer-navigated positioning, robot-assisted) can improve accuracy.

What complications can occur?

Even with optimal technique, there are general and knee-specific risks:

• Impaired wound healing, infection (early/late),
• Thrombosis / pulmonary embolism (reduced by prophylaxis),
• Blood loss / post-bleeding,
• persistent pain or restricted movement (e.g. due to scars, soft tissue problems, malalignment),
• Loosening or implant failure (with long follow-up),
• Instability or patellar problems.

Important point: professional perioperative care (anticoagulation according to risk, wound management, early mobilization) and good rehabilitation significantly reduce the risk of complications.

Expected results & durability

Modern knee prostheses often last for several decades; studies show that a high proportion of total knee replacements remain functional for 15–25 years. Unicompartmental prostheses, when carefully selected, also have very good long-term data; survival rates are encouraging in current reviews and registries. Important factors influencing the outcome are patient age, activity level, surgical technique, implant choice, and postoperative care.

Special notes on unicondylar prosthesis (partial prosthesis)

• Advantages: less bone removal, faster recovery, often shorter hospital stay.
• Disadvantages: Risk that osteoarthritis will later progress in other compartments and revision will be necessary.
• Key: perfect patient selection (isolated, predominantly medial/lateral pain and wear, intact ligament stability, suitable leg alignment).
  Modern studies and analyses confirm very good results in selected patients; however, the surgeon's experience and case volume are crucial for success.

Patellofemoral arthroplasty (PFJ) — when is it appropriate?

Patellofemoral joint (PFJ) arthroplasty replaces only the articular surfaces between the patella and trochlea and is an option for isolated patellofemoral osteoarthritis, especially when conservative treatments fail. It is bone-sparing, can be less restrictive, and, when indicated correctly, can yield very good functional results. However, long-term durability and selection criteria are more challenging compared to total patellofemoral joint replacement (TPR); therefore, a specialized assessment is essential.

Preparing for an artificial knee joint – what you can do yourself

Proper preparation for knee replacement not only improves the healing process but also the long-term outcome. Patients benefit from strengthening their muscles, reducing weight, and learning exercises before the operation. Training with crutches or simple everyday movements (e.g., getting up from a chair, climbing stairs) is also beneficial. The fitter you are before the surgery, the easier the rehabilitation will be afterward.

Living with a knee replacement – ​​what is allowed, what is not?

Many patients wonder which activities are possible again after a total knee replacement or knee prosthesis . Generally speaking, joint-friendly sports such as swimming, cycling, or hiking are recommended and promote mobility. High-intensity sports with many twisting movements or jumps (e.g., soccer, handball, squash), on the other hand, should be avoided or only practiced after consulting with the surgeon. The crucial point is always to avoid unnecessarily overloading the artificial knee joint while simultaneously remaining active.

Second opinion from a knee specialist – why it's important

Deciding to have a knee replacement is a big step. That's why it's worthwhile to get a second opinion from an experienced knee specialist. Specialists like Prof. Dr. Karl Philipp Kutzner at the ENDOPROTHETICUM Rhein-Main in Mainz take the time for a comprehensive consultation, carefully review your findings, and explain the advantages and disadvantages of the various prosthesis models. This ensures that the procedure is appropriate and that you receive the best solution for your needs.

Rehabilitation: this is what the aftercare of an artificial knee joint looks like

Early mobilization (ideally on the day of surgery) is standard practice. A structured rehabilitation plan includes:

• Mobilization and gait training (including stairs),
• Muscle building (quadriceps, hamstrings),
• Mobility exercises,
• Training in everyday life (sitting, stairs, driving a car),
• Pain and thrombosis prophylaxis if necessary, wound checks.

Enhanced Recovery and Assistance Programs (ERAS) accelerate recovery and can shorten hospital stays without compromising safety. Inpatient or outpatient rehabilitation, follow-up physiotherapy, and individualized aftercare are essential for ensuring success.

Quality of life after knee replacement

Most patients report significant pain relief and improved mobility in daily life—many are able to resume walks, cycling, and moderate leisure activities. Sports with increased joint stress (e.g., soccer, high-risk skiing) should be discussed; joint-friendly activities (cycling, swimming, hiking) are usually quite feasible. Managing realistic expectations before surgery increases patient satisfaction afterward.

When is a revision necessary?

Reasons for revision surgery include, for example, infectious complications, aseptic loosening, instability, periprosthetic fractures, or progressive wear in the case of a unicompartmental artery (UAA). Revision procedures are technically more demanding, which is why prevention through careful planning and surgery, as well as early treatment of risks (infections, poor wound healing), is important.

Frequently Asked Questions (FAQ) about artificial knee joints

1. When do I need an artificial knee joint?

An artificial knee joint is advisable when pain and restricted movement persist despite physiotherapy, medication and other conservative measures, and when the quality of life is significantly impaired.

2. What is the difference between a knee prosthesis and a total knee replacement?

Both terms usually mean the same thing: a knee prosthesis replaces worn joint surfaces with implants. The term knee TEP stands for "total endoprosthesis"—here, all parts of the joint are replaced.

3. Are there different types of knee prostheses?

Yes, depending on the findings, there is the unicompartmental knee replacement (UKA) for a partial area, the surface replacement , the total knee replacement (TEP) , and special patellofemoral prostheses (PFJ) that only replace the gliding surface between the kneecap and thigh.

4. How long does knee replacement surgery take?

Typically between 60 and 120 minutes – depending on the type of prosthesis, the diagnosis and the technique used.

5. Is the operation painful?

Not during the operation, as anesthesia is administered. Normal wound and movement pain will occur in the first few days afterward, which can be effectively managed with pain medication. The goal is significant pain relief in the long term.

6. How long does an artificial knee joint last?

Modern implants often last 15–25 years or longer. Durability depends on age, activity level, and the correct choice of implant.

7. Can I play sports again after a knee replacement?

Yes! Sports that are particularly easy on the joints, such as swimming, cycling, or hiking, are perfectly fine. Sports involving jumping and abrupt changes of direction should be avoided.

8. How long does rehabilitation take?

Rehabilitation typically lasts 3–6 weeks, either as an inpatient or outpatient procedure. This is followed by outpatient physiotherapy. Many patients experience initial improvements after just a few weeks, with the final result developing over several months.

9. How long will I be on sick leave after the operation?

For sedentary jobs, the recovery period is approximately 6–12 weeks. For physically demanding jobs, the incapacity for work may last longer. The individual healing process is the determining factor.

10. Does the kneecap always have to be replaced?

No, not always. Whether a patellar component is incorporated depends on the condition of the cartilage and the type of prosthesis.

11. What are the most common risks?

As with any surgery: infections, thrombosis, bleeding, or impaired wound healing. Specifically for the knee: loosening, instability, or restricted mobility. With modern technology and an experienced surgeon, complications are rare.

12. What can I do to contribute to my own recovery?

Regular physiotherapy, exercise in daily life, muscle strengthening, and adherence to medical recommendations are all important. A healthy diet and abstaining from nicotine also promote healing.

13. Can I drive a car with an artificial knee joint?

Yes, usually after 6–8 weeks – as soon as you can move your leg safely and brake without pain. Your doctor will give you the individual go-ahead.

14. Can I have a second artificial joint after a knee replacement?

Yes, if the other knee or a hip joint is affected later, other joints can also be fitted with prostheses. Many patients have multiple endoprostheses.

15. Should I get a second opinion?

Absolutely! A second opinion from a specialized knee specialist like Prof. Dr. Karl Philipp Kutzner at ENDOPROTHETICUM Rhein-Main, Mainz, will give you peace of mind when choosing the right implant.

How to choose the right clinic / surgeon for a knee replacement

• Specialization and number of cases: Centers and surgeons with a high number of cases in knee endoprosthetics usually have better outcome data.
• Transparent information: Benefits, risks, alternatives — everything should be explained clearly.
• A multidisciplinary concept is advantageous: the surgical team, anesthesia, physiotherapy, and rehabilitation structure (short distances to endo-rehab) are all beneficial.

Conclusion: Consultation with a knee specialist is recommended

For expert, individualized advice regarding knee replacement surgery, we recommend consulting a specialized knee specialist such as Prof. Dr. med. Karl Philipp Kutzner at the ENDOPROTHETICUM Rhein-Main . The overall concept at the curaparc Campus in Mainz, with its direct connection to the curaparc clinic and its own ENDO-Reha , represents an integrated care structure that combines surgical excellence with close-knit aftercare – a rarity in today's healthcare system.