When is knee replacement recommended?
Knee replacement surgery, also known as knee arthroplasty, is a surgery that involves the replacement of damaged, worn, or diseased tissues in the knee, specifically the cartilage and subchondral bone, with an artificial joint.
Most patients who undergo this intervention are between 60 and 80 years old, although any adult can be considered a candidate for it.
Once the joint is replaced with a prosthesis, it usually lasts more than 20 years, especially if the new knee is cared for properly and is not put under constant stress.
What is a knee replacement?
The knee prosthesis is made up of two main parts. One of them is attached to the lower part of the femur and another that remains attached to the upper part of the tibia.
But how are they fixed to the bone? Well, both metallic components, usually chrome-cobalt alloys, are fixed to the bone mechanically or directly, or by means of surgical cement.
An intermediate piece of polyethylene is placed between the two metal components, a kind of very resistant “plastic” that allows both components to slide over each other during knee movements.
Types of knee prostheses
The choice of the type of prosthesis will depend on whether the osteoarthritis affects only part of the knee or all of it. Thus, it is not always necessary to change the entire knee, but sometimes it is enough to replace the part of the joint that is damaged.
Therefore, we find three types of knee prostheses:
· Unicompartmental prosthesis: it allows to replace only the part of the knee that is damaged. They are indicated in young patients with osteoarthritis that affects one of the two sides of the knee.
· Total prosthesis: they are the most frequent at present. The entire joint surface is replaced by metallic components that are usually fixed to the bone with a special cement. This prosthesis is the most appropriate when, in addition to the existence of osteoarthritis, the ligaments that support the knee are not in good condition to perform their function correctly.
· Revision prosthesis: in this case, the components of an existing prosthesis are partially or totally changed or removed for new implants.
Regarding the materials that knee prostheses are usually made of, they usually have metal and plastic parts, although other options have now emerged, such as those made entirely of metal or ceramic and those that complement ceramic and plastic.
When is knee replacement necessary?
The knee prosthesis is a surgical option that must be taken into account as a possible solution when the disease or trauma affects the quality of life, as well as the extent to which it prevents carrying out the most common daily activities, either due to pain or the limitation of movements.
In addition to what has already been mentioned, the fact that previous treatments have not worked is also taken into account.
In fact, surgery is usually recommended when other treatments have already been carried out and have not reduced pain or improved mobility. Thus, the knee prosthesis is recommended in the following situations:
· Severe pain, swelling, and stiffness in the knee joint and reduced mobility
· Pain that interferes with quality of life, sleep, and daily tasks, such as shopping or getting out of the bathroom, are difficult or impossible
· Feeling depressed due to pain and lack of mobility
· Inability to work or have a normal social life
On the other hand, it is important to note that advanced osteoarthritis is one of the reasons for deciding to perform surgery to place a knee prosthesis.
Alternatives to knee replacement
Although it is true that when the joint is severely damaged, the only effective solution is to replace the joint with a knee prosthesis, there are certain alternatives that, in many cases, have proven effective:
· Arthroscopic debridement: The instrument (arthroscope) is inserted into the knee, which is then flushed with saline to clean out any remaining bone or cartilage.
· Osteotomy: During an open operation, the tibia bone is cut and realigned so that weight is no longer centered on the damaged part of the knee
· Mosaicplasty: During this procedure, plugs of healthy, hard cartilage, along with some underlying bone from another part of the knee, are transferred to repair the damaged surface
What is knee replacement surgery?
The knee replacement operation consists of replacing the damaged parts of the joint with two components that are fixed to the patient's bone with a special cement loaded with antibiotics. A high-density polyethylene is placed between them that gives mobility to the components, favors sliding and distributes the weight loads.
The prosthesis can also be fixed without cement, but it has been proven that this allows better fixation. It can also be loaded with antibiotics, thus reducing the infection rate by up to 70%. The cementation technique is always essential to achieve a good long-term result.
Knee arthroplasty (prosthesis) takes about two hours and is performed under general anesthesia. When treating, generally, in older people, it is necessary to evaluate the medication that is being taken in order to suspend those drugs that may interfere with the normal development of the intervention, as is the case of anticoagulants, and take into account the associated pathologies in each case.
Recovery after knee replacement surgery
After knee replacement surgery, the patient will be able to walk again in about 24-48 hours, except in cases where pain or some complication prevents walking.
Also, due to the high complexity of the intervention, it is important to acquire an exercise plan for full recovery after your surgery. Approximately 3 to 4 months.
Duration of the knee prosthesis
Knee prostheses are implants that are placed in people between 55 and 65 years of age, since their duration is more than 20 years, as long as their care is adequate. Well, a recent report found that only 2% of knee replacement surgeries require a second surgery within five years of the initial surgery.
But what factors seem to influence the longevity of knee replacements?
· Patient's age. Younger patients tend to be more active. Thus, patients under the age of 50 are likely to have revision surgery.
· daily activity. Some activities may not be appropriate for people with knee replacements. While these activities may not be painful or difficult, they may be putting excessive stress on the prosthesis, causing the parts to wear out more quickly.
· Weight. The more an individual weighs, the more stress is placed on the prosthetic components. Maintaining a normal body weight is of vital importance when it comes to doing a joint replacement.
· Avoiding complications. This may sound obvious, but there are some specific medical conditions that can lead to complications that affect joint replacement.
