An artificial knee joint (knee prosthesis/TKA) is recommended when conservative measures (physiotherapy, medications, injections, weight loss, assistive devices) no longer provide lasting pain relief and improved function, and quality of life is severely limited. The surgery aims to eliminate pain, correct misalignment, and restore mobility. This applies to both total knee arthroplasty (TKA) and partial knee replacements (e.g., sled/unicompartmental)—the choice depends on the extent and location of joint wear and tear, as well as patient factors.

Why the correct indication for a knee prosthesis is so important

The indication —that is, deciding who will benefit from what—is the most important factor for a good outcome. Not every person with knee osteoarthritis automatically needs total knee replacement; in early or unilateral cases, a unicompartmental knee arthroplasty (UKA) or a resurfacing procedure may be more appropriate. Equally important is a careful assessment of concurrent diseases, leg axis, ligament instabilities, and the condition of the patellofemoral joint surface, as an incorrect selection leads to dissatisfied patients, early revisions, or persistent symptoms. Surgeon experience, precise diagnostics (X-rays, MRI if necessary, clinical examination), and individualized patient consultation are therefore crucial.

Types of knee prostheses — briefly explained

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

Total hip replacement (TEP) replaces the joint surfaces of the femur, tibia, and usually also the back surface of the patella with metal-plastic components. It is the standard treatment for advanced, multicompartmental osteoarthritis, deformities, or when multiple joints are affected. Modern implants can be very durable and reliably relieve pain. OrthoInfo+1

2. Sled prosthesis / partial joint replacement

The sled prosthesis replaces only one previously isolated affected compartment (medial or lateral). Advantages: bone-sparing, usually faster recovery, more natural knee kinematics with appropriate 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 arthrosis (PFJ arthrosis), offers a less invasive replacement, and can largely preserve native kinematics. The results are variable—but with careful indication, they are often very good.

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

Before the operation:

• detailed medical history (pain profile, functional limitations, expectations),
• clinical examination (stability, range of motion, leg axis),
• X-ray images in defined planes (stress AP, lateral, oblique views), often supplemented by whole-leg X-rays to determine the axis,
• If necessary, MRI to assess menisci, cartilage and soft tissue, especially in young patients or in cases of unclear findings.

The best treatment option (conservative vs. UKA vs. TEP vs. PFJ) is then decided upon together with the patient. This phase is crucial for success.

Artificial knee joint surgery: Procedure in brief

1. Anesthesia: Regional (spinal/epidural) and/or general.
2. Access and preparation: Bone and cartilage portions are removed according to the selected implant.
3. Fitting the components: Metal components on the femur and tibia, with a polyethylene gliding surface between them. A patella component may be required for patella replacement.
4. Checking the leg axis, soft tissue balance and range of motion.
5. Closure and wound care.

The operation typically takes between 60 and 120 minutes, depending on the complexity and type of prosthesis. Modern approaches (minimally invasive, computer-guided positioning, robotic assistance) can improve precision.

What complications can occur?

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

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

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

Result expectation & 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 excellent long-term data; survival rates are encouraging in recent reviews and registries. Important factors influencing outcome include patient age, activity level, surgical technique, implant selection, and follow-up care.

Special information on unicondylar prosthesis (sled prosthesis)

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

Patellofemoral arthroplasty (PFJ) — when is it useful?

PFJ arthroplasty replaces only the joint partners between the patella and trochlea and is an option for isolated patellofemoral arthrosis, especially when conservative measures fail. It is bone-sparing, can be less restrictive, and, when correctly indicated, delivers excellent functional results. However, long-term durability and selection criteria are more difficult compared to TKA; therefore, specialized assessment is important.

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

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

Living with a knee prosthesis – what is allowed and what is not?

Many patients wonder which activities are possible after a total knee replacement or knee prosthesis . Generally speaking, low-impact sports like swimming, cycling, or hiking are recommended and promote mobility. High-intensity sports involving a lot of twisting or jumping (e.g., soccer, handball, squash) should be avoided or only practiced after consulting the surgeon. It is always crucial to avoid unnecessary overloading of the artificial knee joint and to remain active at the same time.

Second opinion from a knee specialist – why it is important

Deciding to have a knee replacement is a big step. Therefore, it's worth getting a second opinion from an experienced knee specialist. Specialists like Prof. Dr. Karl Philipp Kutzner at ENDOPROTHETICUM Rhein-Main in Mainz take the time to provide a comprehensive consultation, carefully review your findings, and explain the advantages and disadvantages of the various prosthetic models. This ensures that the indication is correct and that you receive the best solution for you.

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

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

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

Enhanced recovery programs (ERAS) accelerate recovery and can shorten the length of stay without compromising safety. Inpatient or outpatient rehabilitation, follow-up physical therapy, and individualized aftercare are all part of ensuring success.

Quality of life after knee replacement

Most patients report significant pain relief and improved daily mobility—many are able to resume walking, cycling, and moderate leisure activities. Sports with increased joint stress (e.g., soccer, high-risk skiing) should be discussed; low-impact activities (cycling, swimming, hiking) are usually possible. Managing realistic expectations before surgery increases postoperative satisfaction.

When is an audit necessary?

Reasons for revisions include infectious complications, aseptic loosening, instability, periprosthetic fractures, or progressive wear in UKA. Revision procedures are technically more demanding, which is why it is important to prevent risks (infections, poor wound healing) through careful planning and surgery, as well as early treatment.

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 mobility persist despite physiotherapy, medication and other conservative measures and the quality of life is significantly reduced.

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 "total knee replacement " stands for "total endoprosthesis"—in this case, all parts of the joint are replaced.

3. Are there different types of knee prostheses?

Yes, depending on the diagnosis, there is the sled prosthesis (UKA) for a partial area, the surface replacement , the TEP (total knee replacement) as well as special patellofemoral prostheses (PFJ) that only replace the sliding bearing between the kneecap and thigh.

4. How long does knee replacement surgery take?

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

5. Is the operation painful?

Not during the surgery, as anesthesia is administered. In the first few days afterward, normal wound and movement pain occurs, which can be easily treated with pain therapy. The goal is significant long-term pain relief.

6. How long does an artificial knee joint last?

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

7. Can I return to sports after a knee replacement?

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

8. How long does rehabilitation take?

Rehabilitation lasts an average of 3–6 weeks, either inpatient or outpatient. This is followed by outpatient physiotherapy. Many patients notice initial improvements after just a few weeks, and the final results develop over months.

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

For sedentary work, approximately 6–12 weeks. For physically demanding work, the inability to work may last longer. This depends on the individual's healing process.

10. Does the kneecap always need to be replaced?

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

11. What are the most common risks?

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

12. What can I do to help my recovery?

Regular physical therapy, daily exercise, muscle strengthening, and following medical recommendations. A healthy diet and abstinence from nicotine also promote healing.

13. Can I drive 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 "goal."

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 treated 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 in Mainz will give you confidence in choosing the right implant.

How to choose the right clinic/surgeon for an artificial knee joint

• Specialization and case volume: Centers and surgeons with a high case volume in knee arthroplasty usually have better outcome data.
• Transparent information: Benefits, risks, alternatives — everything should be explained clearly.
• Multidisciplinary concept: surgical team, anesthesia, physiotherapy, rehabilitation structure (short distances to ENDO rehabilitation) are advantageous.

Conclusion: Consultation with a knee specialist is recommended

For professional, individualized consultation regarding an artificial knee joint, we recommend consulting a specialized knee specialist such as Prof. Dr. Karl Philipp Kutzner at ENDOPROTHETICUM Rhein-Main . The overall concept at the curaparc campus in Mainz, with direct access to the curaparc clinic and its own ENDO rehabilitation center , represents an integrated care structure that combines surgical excellence with close follow-up care—a rarity in today's healthcare system.