Knee Replacement Surgery

What is total knee replacement?

Total knee replacement is one of the most successful and most frequently performed orthopedic operations worldwide. Put simply, it is the replacement of the worn surfaces of the knee joint (as a result of arthritis or injury) with special artificial implants, known as prostheses.

The aim of the operation is not only to eliminate pain but also, at the same time, to correct the deformity of the knee (such as a knee that “leans” inwards or outwards), allowing the patient to regain full function and mobility. The implants used are made of metal alloys (such as titanium or cobalt-chromium) and special polymers (polyethylene), which are fully biocompatible with the human body, ensuring longevity and durability.

Types of implant

Modern total knee replacements are classified according to the way the tibial and femoral components are linked. Historically, there were “hinged” or “constrained” prostheses. Today, however, the prostheses mainly used are of the semi-constrained or non-constrained type, which are also described as surface prostheses.

These prostheses are further divided into:

1. Those that retain the posterior cruciate ligament.

2. Those in which the posterior cruciate ligament is divided and not retained but substituted by a special post on the tibial component.

3. Those in which it is divided and the posterior cruciate ligament is not retained, but its function is reproduced by the geometry of the prostheses.

Neither type of surface prosthesis has clear advantages over the other; the choice of the appropriate prosthesis is strictly individualised on the basis of each patient’s anatomy and needs.

When is the operation performed and what are the indications?

The decision to proceed with a total knee replacement is always taken together with the orthopedic surgeon. The successful outcome of surgery depends to a very large extent on correct patient selection.

The ideal candidate is usually a patient with:

• Severe, constant pain that does not subside with painkillers, hyaluronic acid injections, physiotherapy or weight loss (conservative treatment has been exhausted).
• Loss of joint function: inability to walk any distance, difficulty with stairs or inability to get up from a chair.
• Severe radiographic changes: when the X-ray shows that the cartilage has been completely destroyed (“bone on bone”).
• Specific conditions: the most common are osteoarthritis and rheumatoid arthritis, while post-traumatic arthritis (after old fractures or tears) is not ruled out.

Historically, the ideal candidate was considered to be the slim elderly patient with limited mobility; with modern techniques, however, more and more younger, active patients are undergoing the operation with complete success.

Contraindications

The operation must not be performed (absolute contraindications) if there is insufficiency of the extensor mechanism of the knee, active sepsis (bacterial infection), neuropathic arthropathy (e.g. Charcot joint), or if the knee is completely “locked” and rigid because of advanced damage. Relative contraindications include previous osteomyelitis, severe peripheral vascular disease and various serious coexisting medical conditions that make anaesthesia dangerous.

Before the operation: preparation

The success of surgery begins long before admission to the clinic. Proper preparation reduces anxiety and minimises possible complications.

Before the knee replacement, the patient undergoes a full pre-operative work-up, which includes blood tests, a cardiological assessment (ECG and, where required, an echocardiogram), a chest X-ray and specialised radiographs of the knee (and often of the whole limb) for digital simulation and precise calculation of the implant sizes. If you take medication (such as anticoagulants, aspirin or certain supplements), the doctor will give you precise instructions on when to stop it.

It is also vital to prepare your home for your return: remove rugs and cables you could trip over, place non-slip mats in the bathroom and make sure that everyday items are at an easily accessible height.

The surgical procedure: step by step

Total knee replacement demands tremendous mechanical precision and orthopedic skill.

1. The approach (the incision). Traditionally, the incision was made on the front of the knee and was as long as 20-25 centimetres. Today, the approach is made through a smaller midline or paramedian incision, with the surgeon respecting the fibres of the quadriceps muscle and not cutting them unnecessarily.

2. Correction of alignment and osteotomy. One of the most important steps. If the knee is “crooked” (varus or valgus), this must be fully corrected — otherwise the components will be loaded asymmetrically and will loosen quickly. The goal is for the mechanical axis to pass exactly through the centre of the joint.

3. Perfect balance (Flexion & Extension Gap). The stability of the new joint depends mainly on the soft tissues (ligaments). The surgeon ensures balanced tension of the collateral ligaments throughout the range of motion, creating an equal gap when the knee is bent and when it is straight.

4. Orientation and positioning of the components. The components that “cap” the femur and the tibia are positioned with degree-level accuracy, so that alignment is optimal and the quadriceps works properly. Finally, the smooth “gliding” of the patella in the new metal groove is checked.

The components are fixed to the bone using a special acrylic “cement” (the method of choice in most cases) or without cement (press-fit), an option indicated mainly in younger patients with excellent bone stock. Between the metal components sits the polyethylene, which acts as the new “cartilage” of the joint and must be sufficiently thick (at least 8-10 millimetres) for longevity.

Modern advances: minimally invasive technique (MIS) and robotics

In recent years, MIS (Minimally Invasive Surgery) has revolutionised total knee replacement. Its advantages are significant:

• No muscle damage: the quadriceps muscle is not cut but simply moved aside, resulting in immediate strength in the leg after surgery.
• Smaller incisions and faster healing.
• Minimal blood loss: the need for transfusion approaches zero.
• Minimal post-operative pain, which is fully controlled with modern protocols (Fast Track).
• Very rapid mobilisation: the patient gets up to walk on the very day of surgery.
• Shorter hospital stay, usually no more than 1-2 days.

In combination with robotic assistance or digital navigation systems, the surgeon positions the components with millimetre and degree accuracy, matching them precisely to the “digital footprint” of each person’s anatomy.

The post-operative stage: the first days

As soon as the operation is completed, the patient is transferred to the recovery room. Thanks to modern anaesthetic protocols (usually spinal anaesthesia combined with local infiltration of analgesic mixtures around the knee – LIA), pain is fully controlled. The patient takes their first steps with the help of a walking frame on the very same day — early mobilisation is the “key” to avoiding complications such as thrombosis and to faster recovery of the muscles.

Rehabilitation and recovery

The success of the operation is owed 50% to the surgeon and 50% to the patient. In the first days a continuous passive motion (CPM) machine is often used, which bends and straightens the knee slowly and painlessly, preventing the formation of adhesions. The aim is for the post-operative range of motion to reach at least from 0 degrees (full extension) to 100-110 degrees (satisfactory flexion).

The physiotherapy programme: rehabilitation starts immediately and includes isometric quadriceps exercises, active flexion and extension exercises, as well as strengthening and proprioception exercises.

As for the return to everyday life:

• Walking: with a walking aid for the first 2-3 weeks, while at around 4-6 weeks most patients walk independently.
• Driving: usually after the 4th-6th week, provided full control has been regained and strong painkillers are not being taken.
• Sport: low-impact activities (swimming, stationary cycling, walking) are encouraged, while contact or high-impact sports are best avoided.

How long do the operation and the hospital stay last?

Total knee replacement usually takes one to two hours, depending on the complexity of the case and the degree of deformity that needs to be corrected. Thanks to modern minimally invasive techniques and rapid recovery protocols (Fast Track), the hospital stay has been reduced dramatically compared with the past: in most cases it does not exceed one to two days.

This short stay is not merely a matter of comfort — a rapid return to familiar surroundings, combined with early mobilisation, reduces the risk of complications from prolonged bed rest and contributes to the patient’s psychological and physical recovery.

Possible complications

With modern MIS techniques, complication rates are extremely low:

• Infection: only 1-2% worldwide. For prevention, prophylactic intravenous antibiotics are given and operations are performed in state-of-the-art theatres (laminar flow).
• Thromboembolic disease: 0.5-2%. Immediate mobilisation, anti-embolism stockings and anticoagulant medication almost eliminate the risk.
• Neurovascular injury: extremely rare (below 0.05%).
• Blood loss and skin problems: minimised with minimally invasive methods.

Any symptoms (marked swelling of the calf, fever, sudden pain) must be reported immediately to the treating doctor.

Before and after the operation

Before the operation, the patient lives with chronic pain, deformity and severe restriction of movement, with everyday life dictated by the limits set by the worn knee. After the knee replacement and completion of rehabilitation, most patients regain pain-free movement and return to activities they had given up — walking, travelling, swimming, dancing. Correction of the deformity also restores the correct alignment of the limb.

Cost of knee replacement

The cost of total knee replacement is not uniform, as it depends on the type and materials of the implants, whether or not robotic assistance is used, the hospital and room category, the length of stay, and the patient’s insurance cover — private insurance policies and insurance funds cover a significant part of the expense in most cases.

Precise information on cost is always provided on an individual basis, after the clinical examination and once the treatment plan has been defined. The practice is at your disposal for any relevant information and for guidance in dealing with insurance companies.

More on the factors that determine the cost and on cover by insurance funds: Cost of surgery.

Frequently asked questions

How many years does an artificial joint last?

With modern materials, durable polyethylene of substantial thickness and perfect mechanical alignment (robotic/MIS navigation), today’s prostheses generally last 15 to 20 years, and in many cases for life. The key is avoiding excessive friction and ensuring symmetrical loading.

Is the operation painful?

Thanks to modern anaesthetic protocols (Fast Track), specialised analgesia (nerve blocks, LIA) and minimal muscle trauma (MIS), post-operative pain is controlled and mild — it feels more like “tightness” and heaviness than sharp pain.

Can I have both knees operated on at the same time?

In some cases, provided the patient is healthy and has no serious cardiac or respiratory problems, both knees can be replaced at the same time. This is decided strictly after a full medical assessment by the orthopedic surgeon and the anaesthetist.

Will I need physiotherapy at home?

Yes. Physiotherapy during the first weeks is essential. You will learn how to walk correctly, how to go up and down stairs (we go up with the “good” leg and down with the “operated” leg) and how to strengthen the muscles of the leg.

When will I walk after the operation?

With modern MIS techniques, mobilisation begins on the day of surgery with the help of a walking frame. Independent walking is achieved gradually, usually within 4-6 weeks.

Will I set off airport security scanners?

The metal components of the prosthesis may trigger metal detectors. It is usually enough to tell the security staff that you have an artificial joint; the doctor can also provide you with a relevant certificate.

Is the cost covered by insurance?

In most cases, private insurance policies and insurance funds cover part or all of the expense. The practice can give you detailed information and guide you through the process.