Knee prosthesis

Knee arthrosis

From this point, you decide, or maybe you have already decided, if you want a knee surgery.

Fitting knee prosthesis is among the most common orthopaedic interventions (300,000/year in the United States and 50,000/year in France). Your worn knee joint is replaced with an artificial knee joint, what we call a prosthetic knee. The purpose of such intervention is to alleviate your pain occasioned by aworn joint.


Arthrosis and prosthesis

Like all joints, knee includes a cartilage dressed-surface and two menisci intended for damping shocks and allowing fluid and smooth movements. This cartilage can become worn: this means arthrosis.

We can compare this wear with tire wear, when a tire become smooth after thousands of miles. Sometimes they are reconditioned, re-treaded! Going forward with the comparison, a prosthetic knee is a “re-tread” worn knee.

Cartilage wear may be accelerated by various factors. Most commonly, arthrosis means spontaneous cartilage aging.

Wear knee is a common condition, because it is a solicited joint, which is subject to a lot of pressure.

The liquid in the joint maintains cartilage vitality and“washes” this cartilage surface at all times. Over time, the joint cartilage becomes less elastic and dried. Cracks occur and cartilage becomes irregular. Bone is no longer covered by cartilage. It is bare. In the end, bone surfaces are in direct contact. This triggers violent pain. The knee is deformed (X-or O-shaped position).

A total knee prosthesis is composed of several parts:

– Femoral metal piece (cobalt chromium alloy or titanium) which is fixed to the femur, with or without cement,

– A metal tibial piece, which is fixed to the tibia, with or without cement,

– An intermediate piece of polyethylene, which is interposed between the two metal components.

Polyethylene implantsare most often used for patellar replacement.

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Alternatives to prosthetic knee replacementOther interventions can sometimes be proposed before mounting a prosthetic knee. It all depends on age, severity of wear and knee deformation, occupation, the presence of other diseases, etc.

Non-surgical treatments include painkillers and anti-inflammatory drugs, physical therapy, sometimes changing footwear or stabilizing the knee using special splints (orthotics), and injection of anti-inflammatory drugs or hyaluronate (liquid which is normally found in the joint) into the joint.

Arthroscopy is a minimally invasive surgical procedure; knee can be cleaned, debris removed, and cartilage grafted. These allow us to obtain a full picture of the damage in order to choose the most suitable prosthesis.

Osteotomy is a surgical procedure in which the calf bone is realigned; a more worn compartment of the knee is thus relievedand the pain disappears. This intervention is rarely recommended after 60 years of age.

Mono-compartmental prosthesis is a half-prosthesis that allows replacing only the worn part of the knee. The surgeon must be sure that wear does not affect all compartments of the knee. The life of a half-prosthesis is shorter, but if the indication was appropriate, recovery after surgery is much faster, because the internal ligaments of the knee remain intact. On the contrary, if wear of other compartments continues, we should expect a new intervention with a full prosthesisafter a few years.

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When does the surgery must be decided?

The answer is“when we are the worst”!
Pain is the rationale of a surgical decision.

There is no reason to operate too early if impact is not too high. But, knowing the quality of results that we could expect in 2016, it would be a shame (especially if you are active) not to take advantage of a prosthetic knee, when knee pain and deformation are important.

Before intervention

When the decision was made for fitting a prosthetic knee, a pre-anaesthetic consultation is provided, as for any other surgery. This is to assess the health status of the patient. If needed, the anaesthesiologist will recommend blood and urine tests, an ECG or consult another specialist (e.g. a cardiologist or pulmonologist). A summary of this assessment is clearly presented to the patient and his/her family (when the patient is older), for the decision to be taken knowingly. Intervention may be postponed sometimes (rarely). During this consultation, the anaesthetist will inform you about the different types of anaesthesia that can be applied to your specific case.

Sometimes this pre-surgery summary is performed during a hospital stay of several days before surgery. This formula is applied to patients with multiple associated diseases.

Physical therapy sessions conducted before intervention,leads to quicker recovery after surgery.

Certain medications should be discontinued before intervention to prevent any interaction with either anaesthetic or coagulation drugs. Any treatment change or interruption will be organized, scheduled, with a possible substitution treatment, by the anaesthesiologist during the pre-anaesthesiology consultation.

Anaesthesia should be epidural or intra-spinal (the two legs are blocked), local (only the nerves that go to the knees are blocked) or general anaesthesia.



Rehabilitationmay be commencedfrom the intervention evening, when pain treatment is effective. This entails slight and manualknee mobilizationperformed by the physical therapist, associated with passive movements performed using electrical mobilization equipment.

In the evening of intervention, patientsmay be able to start moving their feet and anklesalone, and contract their calf muscles.

You will be placed in a chair 48 hours after surgery and asked to make your first steps. Support is generally fully authorized in the first days after surgery. First, you will use a crutch to facilitate your first steps. Gradually, you will resume your normal walk. You will also be less supported. Physical therapist will help you walk with crutches.

Rehabilitation will include exercises that allow recovery of knee mobility, muscle strength, especially of the quadriceps and calf muscles, and regaining walking reflexes with a new knee. It is desirable the patients reach 90° of flexion at 7 to 10 days after surgery.

Patients may generally leave the hospital between the 10thand 15thday after surgery, continuing physical therapy at home or in a rehabilitation centre. Typically, you leave the hospital when:

  • You can walk with crutches for short-distance, safe and with no help
  • Operative wound scars well.
  • You can climb stairs using crutches

At home

Local care from a licensed nurse is mandatory. Dressingswill be changed twice/day until the wound is healed. Stitches will be removed after 16 days. Injections of anti-coagulant will be continued for one month after surgery. When you are at home, you have to take care of the “new knee”. At first, the area around the wound will be hot and swollen. You can reduce knee pain and inflammation with ice and cold applications. You can sleep in any position you want.

Your physical therapist will help you strengthen your muscles, improve mobility, reduce the use of crutches, and achieve full recovery as well as possible.

You should not place a pillow under your knee when you lay in bed. This could lead to difficulties of extension recovery. When you sit on a chair, hold your knee stretched by placing your foot on a stool. You will avoid a vicious position in flexion.

Driving: you are allowed to drive usually after the 6thweek. You are allowed to ride a bicycle when you can walk properly without crutches, normally after about six to eight weeks. You are allowed to swim when the wound is completely healed, normally after about four to eight weeks.

Patients will be encouraged to stay active, keep the same lifestyle, practice sports (golf, walking, cycling, swimming), but avoid contact sports. With a prosthetic knee, jogging, tennis, skiing or sports of combat are not advised. Knee recovery will be complete in 6 to 12 months after the intervention.

Your surgeon will conduct a full check-up at the end of 2 to 4 weeks with a control X-ray.

Possible postoperative complications

Results largely depend on the ability of the surgeon. US studies have shown that results are better if a surgeon applies at least six knee prostheses per year and at least 25 prostheses are applied within a department per year. Complications are not a rule!!! But… there is no risk-free surgery!!!

Surgery is more difficult in obese patients. Fitting a prosthetic knee is not an anodyne intervention. If surgery is performed before 60 years of age, it will often require another later intervention to replace the worn components.


During the first week after surgery, the origin of fever is often the operation itself; if fever persists, however, it is a sign of inflammation or infection.


It rarely requires surgical evacuation.

The joint becomes red, swollen and painful. Putting ice will make the knee less swollen.

Infection of the surgery site

If diagnosed early (within the first 3 weeks), it generally requires rigorous antibiotic intravenous treatment. Patientsexhibit fever, their knee pain returns, and the wound becomes red and inflamed. When the infection is deep and touches the prosthesis, articular lavage should be performed via arthroscopy. Diagnosed too late, it sometimes requires a surgery to remove the implants followed by re-implant of a new prosthesis. Infections in other parts of the body – e.g. tooth infections or urinary infections – can cause infection of the knee prosthesis. Consequently, when you must undergo dental interventions, we advise taking antibiotics as a preventive measure.


Knee swelling and calf immobility are the origin of blood stagnation and increasing risk of clots. In the event of a thrombosis, an (undesirable) blood clot is formedin a blood vessel, most often in a vein. Calf becomes very painful. You should contact your doctor or go to the ER.

Prosthesis mobilization

With time, the prosthesis can come off faster than anticipated and require re-intervention. Then, it must be replaced by a new prosthesis. In addition, the current total knee prostheses have a longer lifespan, on average 15-20 years.

Pain around the patella

Sometimes the patella does not work well or remains very sensitive. Knee folding and stretching are very painful. This pain decreases with time.

Knee stiffness

It occurs later, being characterized by limitation of movement, whether extension or flexion, despite physical therapy sessions. In case of stagnation or insufficient recovery of mobility, mobilization can be recommended under general anaesthesia.

Loss of sensation in the front side of the knee

It is due to the severance of the small nerves found in the skin. Even if the skin sensitivity around the scar is not always fully recovered, it is rarely disturbing.



Fitting knee prosthesis is a frequent surgical intervention with enormous benefits. The indication is provided by the orthopaedic surgeon according to the progress of arthrosis. Fittings of prosthetic knees or shouldersare considered to be the interventions that have revolutionized the orthopaedic world the most in the last century.


Pain accompanies the wear knee joint and is the main reason that will lead to seeing a specialist. This pain is most often felt through the entire knee; sometimes, it is felt only at the bottom, at the inner part or behind the patella.

At first, patients only experience pain when they are standing up after sitting for a while. After walking some steps, pain alleviates; it is the joint “revival” pain. Pain is also felt when climbing or descending stairs. When wear amplifies, pain can persist even during rest, and then it progresses to waking us up at night.

At first, we feel stiff especially after night, i.e. morning stiffness. Knee stiffness intensifies progressively. Patients may have problems putting shoes on and getting dressed.

Walking is difficult and distance walked with no pain decreases from day to day.

When wear becomes severe, patients will limp. Finally, the pain becomes so severe that patients will have to use crutches to walk.

Why surgery?
With time, these localized arthroses risk to worsen progressively.

At first, pain decreases after taking medication. Progressively, pain will no longer respond to any treatment. Patientsmay have difficulty walking, running, and may gradually give up visiting their families or friends.

The assessment of the right moment to implant prosthesis depends on age, the importance of pain and disability (increasing walking difficulties because of the pain). Surgery is chosen by the surgeon and the patient when other treatments no longer provide results and when the pain becomes too acute, especially at night. The purpose of intervention is to eliminate pain, improve mobility of the knee and provide patients a better quality of life.

Patients subjected to this intervention will undergoX-ray tests. Surgery is not recommended for those with skin infections, paralysis or general malaise.

Intervention is conducted under general or local anaesthesia. It is followed by treatment with painkillers, which is currently at the forefront of the concerns of medical teams, and often allows quasi-complete pain alleviation.

6 months after surgery, progress is stabilized; walking becomes normal, without limping, and pain is completely attenuated.

Currently, the life of a prosthetic easily reaches 20-25 years. This explains the current surgical world enthusiasm to treat a disease that 20 years ago still led to complete disability, with loss of autonomy.

Some answers to your concerns…

The procedure will last 1.5 hours. It willbe practised in an OR with a sterile laminar flow enclosure. During the intervention, patients will receive medication to induce sleep. Patients will not feel anything in the knee, regardless the chosen type of anaesthesia. They will receive antibiotics (for 48 hours) to minimize any risk of possible infection.

The incision on the front of the knee measures on average between 10 and 15 cm. After opening the joint, damaged bone and cartilage are removed and prosthesis will be implanted. The type of implant will be chosen by the surgeon, depending on several variables.

Gains in knee prosthesis assembly and design techniques allow for the implantation of prosthetic knees with shorter incisions (minimum approach). New prosthetic concepts allow recovery of approximately 130° flexion!!

After intervention
ICU: patientsare broughtto the ICU after surgery, for supervision. Patientsmust stay 2 hours there to ensure theircomplete waking up.

Painkillers have made great progress in the field of joint surgery.

Well-managed pain protocols can help patients to avoid any postoperative pain. Sometimes patients can control their own pain. They must push a button (of an automatic syringe) and inject a dose of painkiller, depending on the intensity of pain.

Ice will be placed around the knee after surgery to reduce swelling. Drainage is applied generally, to avoid bruising; drainage is removed between the second and third day. We often use blood recovery. Blood extracted from the joint drainage after surgery can be re-transfused to patients within 6 hours after surgery!

Blood fluidity is increased to prevent unwanted blood clots in the calf veins. Patientsreceive anticoagulant injections once a day for a month

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