Types of knee prosthesis

• A knee replacement is an artificial structure used to replace the damaged joint.
• Knee replacement may be partial (unicompartmental), total (tricompartmental) or revision.
• The specialist will take into account factors such as age, joint mobility and bone wear to recommend one type of prosthesis or another.

Knee prostheses are the artificial elements and structures that are implanted during an arthroplasty, with the aim of replacing the normal structure of a knee.

The reason for the decision to implant a prosthesis is osteoarthritis of the knee. In fact, the most common candidates for this intervention are people over 60 years of age, being a profile more prone to suffer from the disease in its most advanced stage.

Total or partial arthroplasty is a fully recommended procedure when conservative methods (medication, infiltrations, physiotherapy, etc.) are not effective. In fact, the main advantage of fitting a knee prosthesis is to improve the patient's quality of life by reducing pain and increasing the mobility of the joint.

Knee replacements last on average 15 - 20 years. 

However, it is not possible to predict exactly how long it will take before the prosthesis needs to be replaced, as in some cases, they last more than 25 years and in others, it is never necessary to replace them.

The choice of the type of knee replacement will vary depending on the trauma situation and the surgical need, as it is not always necessary to replace the entire knee. Sometimes it is sufficient to replace only the joint that is damaged.

The specialist will therefore examine whether the joint wear or osteoarthritis has occurred in one part of the knee or, on the contrary, affects the entire knee, in order to choose between a unicompartmental or tricompartmental knee replacement.

The unicompartmental knee replacement is indicated when degenerative or traumatic osteoarthritis has damaged only one side of the joint. In this case, the knee is not affected as a whole and the prosthetic replacement is limited to the damaged regions.

Unicompartmental arthroplasty is not performed as frequently, as it does not prevent the progression of osteoarthritis in the rest of the joint. 

However, it should be added that the components used are the same as those used in tricompartmental arthroplasty, but in the case of the partial prosthesis, only the damaged end is implanted.

During the procedure, small incisions are made to remove damaged tissue and bone. For this reason, thanks to the minimally invasive surgery, the recovery time will be shorter than after total arthroplasty.

Tricompartmental arthroplasty is more common than partial knee surgery. During total knee replacement surgery, the entire joint is replaced.

The main reason for the intervention is to improve the quality of life of the patient, who may either have suffered a fracture or otherwise suffers from advanced osteoarthritis.

Advanced osteoarthritis is the most common cause of total knee replacement.

In addition, resorting to surgery means that previous treatment with medication, physiotherapy or infiltration has had no effect due to the advanced stage of the disease.

In fact, most patients who undergo total knee arthroplasty are people between 50 - 80 years of age with constant pain in the joint and with a high disability to move the knee. However, it is important to add that successful total knee replacements have also been performed in younger people, although these cases are very rare.

The total knee prosthesis is attached to the bone by means of a tibial tray between the tibia and the femur. A piece called an insert (polyethylene) is placed on it to facilitate the articulation of the femur and tibia, by means of the femoral component (metal).

Revision knee replacement is a procedure that is performed when the patient has already undergone knee replacement surgery. The aim is to replace worn prosthetic components with new components.

Typically, total prostheses, also known as tricompartmental prostheses, are implanted. However, in this revision surgery, engineered implants are also used, as there are often specific problems with stability and lack of bone.

Therefore, this type of surgery is intended for patients with poor prosthetic stabilisation, as well as for people who have major bone defects that can lead to joint instability.

During knee arthroplasty, the specialist may replace the joint with cemented or uncemented fixation. As you would expect, this decision is made prior to surgery, and after visualising the condition of the bones.

It is important to know that the type of fixation performed is not better than the other, as each patient will need one or the other, depending on the situation they present.

However, in deciding which prosthetic fitting is correct, the doctor will take into account factors such as:

• Age
• Weight
• Bone strength
• Frequency of exercise

Cemented joints

In the case of cemented fixation arthroplasty, the surgeon will use a special bone cement to help hold and fix the components of the artificial joint in place.

Cemented prostheses are indicated and recommended for older and more physically active people.

Uncemented Joints

In cementless prosthesis, the artificial joint components are made of a porous material, which allows the bone to grow naturally.

Uncemented joints are stronger and more permanent attachments than cemented joints. For it is the bone itself that, as it grows, fills in the space and creates a stronger attachment.

Therefore, uncemented joints are less likely to weaken over time.

If you would like to assess your knee problems and study the possibility of a prosthetic need, we remind you that, through Operarme, you can book a first appointment with our specialist in Orthopaedic surgery by clicking on the following banner: