A total knee replacement is a surgical procedure whereby the diseased knee joint is replaced with artificial material. The knee is a hinge joint which provides motion at the point where the thigh meets the lower leg. The thigh bone (or femur) abuts the large bone of the lower leg (tibia) at the knee joint. During a total knee replacement, the end of the femur bone is removed and replaced with a metal shell. The end of the lower leg bone (tibia) is also removed and replaced with a channeled plastic piece with a metal stem or a separate plastic and metal shell (depending upon type of implant used).
The posterior cruciate ligament is a tissue that normally stabilizes each side of the knee joint so that the lower leg cannot slide backward in relation to the thigh bone. In total knee replacement surgery, this ligament is retained, sacrificed, or substituted by a polyethylene post. Each of these various designs of total knee replacement has its benefits and risks.
Which patients should consider a total knee replacement?
Total knee replacement surgery is considered for patients whose knee joints have been damaged by progressive arthritis, trauma, or other rare destructive diseases of the joint. The most common reason for knee replacement in India is severe osteoarthritis followed closely by Rheumatoid arthritis of the knees.
Regardless of the cause of the damage to the joint, the resulting progressive pain and stiffness, and decreasing daily function often leads the patient to consider total knee replacement. Decisions regarding whether to undergo knee replacement surgery are not easy. Patients should understand the risks as well as the benefits before making these decisions. A detailed discussion with your surgeon will help arrive at a decision especially when there are so many implant choices now available.
This factsheet is for people who are considering having a knee replacement operation. A knee replacement replaces damaged or worn parts of the knee joint with a prosthesis made up of metal and plastic parts. Depending on the condition of your knee, a "total" or a "half" knee replacement may be done. In a half knee operation, only the inner or outer half of your knee is replaced. A total knee replacement is more commonly done.
Why have knee replacements?
Your knee joint is made up of the ends of the thigh bone (femur) and shin bone (tibia), which normally glide over each other smoothly because they are covered by smooth articular cartilage. The joint is held in place by ligaments and covered at the front by the patella (kneecap). If the cartilage is damaged by injury or worn away by arthritis for example, the ends of the bones can rub together, causing pain and restricting movement. If this happens, your knee joint can be replaced with a prosthetic one.
Types of knee replacement
There are several different types of knee replacement. Some need special bone cement to keep them in place. Other types of artificial knee parts are coated with a chemical which encourages bone to grow into it to hold the components in place
Your surgeon will discuss the various options with you.
What are the alternatives?
Surgery is usually recommended only if non-surgical treatments such as taking medicines to reduce pain and inflammation or using physical aids such as a walking stick do not help to reduce pain or improve mobility.
What happens before a full knee replacement?
Your surgeon will discuss how to prepare for your operation. For example, you may be asked to give up smoking as it increases the risk of you getting a chest infection and slow the healing of your wounds.
A knee replacement takes one to two hours.
It is usually performed under an epidural anesthetic, which means that you will be awake throughout the procedure and will feel no pain. Once the anesthetic has taken effect, an incision, usually around 10-30cm (5-7 inches) long will be made down the front of your knee. The length of the incision may be shorter depending on the technique your surgeon is using. Your kneecap will be moved to one side so the joint can be reached. The worn or damaged surfaces will be removed from both the end of your thighbone and the top of your shin bone. The surfaces will then be shaped to fit the knee replacement. The replacement parts will be fitted over both bones. Sometimes the part of your kneecap that is in contact with the new knee joint is replaced with a plastic prosthesis. This is called patellar resurfacing. After the new parts are fitted and tested to make sure they move smoothly, your surgeon will close the wound with stitches or clips and cover it with a dressing.
After the operation
You will be given painkillers to help relieve any discomfort as the anaesthetic wears off. If you had an epidural anaesthetic, you may not be able to feel or move your legs for several hours after your operation. You won't have any pain in your legs. Starting from the day after your operation, a physiotherapist usually visits you every day to help you do exercises designed to help your recovery. People generally stay in hospital for 5-10 days. After this time, you will be able to walk with sticks or crutches. Before discharge, your nurse will give you advice about caring for your stitches, hygiene and bathing.
Recovering from a Knee Replacement
Once home, you should take painkillers if you need to, as advised by your surgeon or nurse. The exercises recommended by your physiotherapist are a crucial part of your recovery, so it's essential that you continue to do them. Most people find that they are able to move around their home and manage stairs, but some routine daily activities will be difficult for a few weeks. You must follow your surgeon's advice about driving. You shouldn't drive until you are confident that you could perform an emergency stop without discomfort. You can go back to work after about six weeks if you have an office job. However, if your work involves a lot of standing or lifting, you should stay off for longer (usually about three months).
Your knee will continue to improve over a period of at least six months.
Deciding on Treatment
A knee replacement is a commonly performed and generally safe surgical procedure. For most people, the benefits are far greater than the disadvantages. However, in order to make a well-informed decision and give your consent, you need to be aware of the possible side-effects and the risk of complications.
Side-effects are the unwanted but mostly temporary effects of a successful procedure, for example, feeling sick as a result of the general anesthetic. Anyone having a knee replacement can also expect the side-effects listed below.
Your knee may be sore when you move it and swollen for up to three months.
There will be a scar (8-12 inches long) over the front of the knee. The scar and the outer side of the knee may be numb, which can sometimes be permanent.
Complications are unexpected problems that can occur during or after the procedure. Most people are not affected. The main complications of any operation are bleeding during or soon after the procedure, infection and an abnormal reaction to the anesthetic.
Specific complications of knee replacement surgery are rare but can include those listed below:-
* The wound or joint can get infected. Antibiotics are given during surgery to help prevent this.
* Sometimes it is not possible to make the new knee fully stable and you may need to have a second operation.
* The operated leg may be a slightly different length. Sometimes, a raised shoe on the shorter side is necessary.
* Nerves in the leg can get damaged during the operation but this is very rare.
* A build-up of scar tissue occasionally restricts movement. Another operation may be performed to break down the scar tissue. In rare cases, the loss of movement may be permanent.
* The kneecap can become dislocated after knee replacement surgery. Once again this is rare if the technique is good and implant selection is appropriate.
* For up to six weeks after the operation, it is possible to develop a blood clot in the veins of the leg (deep vein thrombosis or DVT). This clot can break off and cause a blockage in the lungs. In most cases this is treatable, but it can be a life-threatening condition. Most people are given medicines and/or compression stockings to wear during the operation to help prevent a DVT.
The chance of problems depends on the exact type of operation you are having and other factors such as your general health. Your surgeon will explain how the risks apply to you.
A knee replacement usually lasts for at least 10 – 15 years or more, after which you can have a revision operation to replace it. However, revision operations are more complicated than original knee replacements, and the results are not always as successful.
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