Indication for artificial knee joint

To make the decision to install an artificial knee joint easier, there are defined indications as to when the installation of an artificial knee joint is advisable. In principle, conservative therapy with painkillers and physiotherapy should be started for a diseased knee joint. However, if these therapeutic options have been exhausted and have not produced any effect, the physician can make an indication for the installation of an artificial knee joint.

The most common symptoms of osteoarthritis are pain during movement, but pain at rest is also possible in an advanced stage. These rest pains occur particularly frequently during the night. Patients may also notice a certain stiffness in the joint.

Overall, the quality of life of the affected patients is significantly reduced. The most common indication for an artificial knee joint is the so-called degenerative wear and tear of the joint. The bone surfaces of a joint are covered with a protective layer.

This protective layer consists of cartilage tissue. This layer serves to ensure that the joint can be moved smoothly and without pain. If this layer of cartilage is increasingly worn away with age and eventually becomes completely absent, bone comes into permanent contact with bone, causing severe pain in the knee.

In the meantime, arthrosis is no longer just a problem of old age. More and more young people are also affected. Be it through an accident or a sports injury.

Knee joint arthrosis can also be caused by malpositioning of the feet or legs, overloading, previous operations or chronic overweight. There are different types of artificial knee joints. Depending on the extent of the damage to the knee joint, different types of artificial knee joint are used.

If only a certain side is worn out or destroyed, only this side needs to be replaced by artificial material. So-called partial prostheses are used for this purpose. These are also called sled prostheses, because they look like the runner of a sled.

If the cartilage and bone tissue is defective not only in one place but in several, then a different variant of the artificial knee joint is used. This variant is called a so-called full prosthesis or total prosthesis. Since ligament structures are also involved in the stability of the knee joint, they also play a role in the choice of the artificial knee joint.If the ligamentous apparatus is intact and thus not damaged, uncoupled prostheses can be used.

Even in humans, the upper and lower leg do not have a firm and guiding connection with each other. If the ligamentous apparatus is already somewhat damaged, so-called partially coupled prostheses are used to compensate for the loss of stability. In some cases, the ligamentous apparatus is so damaged that it can no longer perform its stabilizing function of the knee joint.

In these cases, fully coupled types of artificial knee joint are used. In order to understand the different types of artificial knee joint in more detail, it is necessary to consider the structure of the knee joint. The knee joint is formed by the thigh, the lower leg and the kneecap.

The part of the thigh that is involved in the knee joint is formed by two sliding rollers, also called condyles. There is an inner and an outer roller. The lower leg forms a plateau for these rollers as a counterpart.

The two disc-shaped menisci serve as a sliding bearing and buffer. The back of the patella is only in contact with the thigh, but not with the lower leg. With the so-called sled prosthesis, usually only one role of the thigh is replaced, i.e. only one condyle.

The type of prosthesis is then called unicondylar hemicycle. If both rollers are replaced, the type of artificial knee joint is called a bicondylar sled prosthesis. The unilateral sled prostheses are usually unguided.

This means that these prostheses are placed exactly at the point where they are defective. They therefore only replace one structure. For unguided types of sled prosthesis, the ligaments of the knee joint must be intact so that they can continue to guide the joint.

So if the ligaments are not intact in addition to the joint, the prosthesis must be at least partially or even fully coupled. In this case, the prosthesis not only replaces the defective surface structure, but must also take over the function of the ligaments. Fully coupled prostheses are axis-guided and are used as part of a full prosthesis if both the thigh and the lower leg need to be treated as well, since all structures are damaged.