When is a knee prosthesis placed?
A knee prosthesis (= an artificial knee) is placed in cases where there is severe damage to the knee joint. The cause of this damage is usually osteoarthritis or rheumatism. This causes pain and a malfunctioning of the knee joint. The damage is visible on an x-ray of the knee.
Your knee is a hinge joint consisting of 3 parts: the lower femur, the upper tibia and the patella. The ends of the femur and the tibia are covered with a layer of cartilage. This is elastic and absorbs bumps and bruises, so the knee can move smoothly.
Between the two bones are the inner and outer meniscus, which also absorbs and reduces the friction in the knee.
The knee joint capsule encloses the whole joint and ensures that the joint fluid lubricates the cartilage. This fluid also causes less friction in the knee. In the middle of the knee is the anterior cruciate ligament.
This prevents the lower leg from moving out too far while a person is walking or turning around. The knee joint is then covered by the kneecap.
Wear to the cartilage is called osteoarthritis
Such wear is a normal aging process that occurs in all people.
Wear takes place faster in some people’s joints. This is often caused by carrying heavy loads, accidents or deformities of the knee joint.
There is also a possibility that a weak or deformed joint may be hereditary.
Wear of joints cannot always be attributed to a specific cause. Wear to joints causes pain.
When pain cannot be managed by other methods, a knee replacement is proposed.
The knee prosthesis
There are two types: the total and the half knee prosthesis. The most common is the total knee prosthesis, which replaces all the cartilage of the femur and the tibia.
If only the inside or outside of the knee has to be replaced we use a half knee replacement (also called a hemi-knee replacement prosthesis or a unicondylaire prosthesis).
There is also a special knee prosthesis available that is adapted for use by women. A knee replacement is a serious operation that requires much willpower and effort from the patient to be successful, but with good preparation you can avoid unnecessary tension and disappointment.
During the surgery you are given antibiotics to reduce the chances of infection. The procedure takes about 1.5 hours. When the operation is done, the knee is opened at the front by a vertical cut of about twenty centimetres. The surgeon removes the damaged joint surfaces.
Special instruments are used to adapt the bones to the shape of the prosthesis so that the prosthesis can be well anchored. A plastic disk placed between the metal parts of the prosthesis allows the knee joint to pivot smoothly. Generally no patellae prosthesis is inserted because special adaptation to the person’s own patella ensures that there are hardly any problems with the patella once the knee replacement has healed.
In America, experience has indicated that the placement of artificial patellas has a long term and short term complication risk of approximately 10% of all cases. Thus a patella prosthesis is only placed when it is necessary and it is mostly necessary in cases of serious wear to the patella or serious instances of rheumatism.