Knee replacement involves replacing a knee joint that has been damaged or worn away, usually by arthritis or injury.
Your knee joint is made up by the ends of your thigh bone (femur) and shin bone (tibia). These normally glide over each other easily because they are covered by smooth cartilage. If your cartilage is damaged by injury or worn away by arthritis, for example, it can make your joint painful and stiff.
A new knee joint usually improves mobility and reduces pain, although your new knee will not be able to bend quite as far as a normal knee joint.
Depending on the condition of your knee joint, you may have part, or all, of your knee joint replaced. A total knee replacement is more common.
Artificial knee parts can be made of metal and/or plastic. A knee replacement generally lasts for up to 15 years but can last as long as 25 years.
Surgery is usually recommended only if non-surgical treatments, such as physiotherapy and exercise, taking medicines or using physical aids like a walking stick, no longer help to reduce pain or improve mobility.
If you do require surgery, your surgeon will explain your options to you.
Alternative surgical procedures include:
You may have already had these procedures before your knee replacement.
Your surgeon will explain how to prepare for your operation. For example if you smoke you will be asked to stop, as smoking increases your risk of getting a chest and wound infection, which can slow your recovery.
The doctors may also temporarily stop some of your other medications or change them until your surgery is complete (for example your pain killers may be replaced with ones that do not interfere with the anti-blood clotting drugs that may be given to you for the surgery). You will also be given antibiotics at the time of surgery and for a short period after it to prevent infections.
The operation usually requires a hospital stay of 7 to 10 days and it's done under general anaesthesia. This means you will be asleep during the operation. Alternatively you may prefer to have the surgery under spinal or epidural anaesthesia. This completely blocks feeling from your waist down and you will stay awake during the operation.
If you’re having a general anaesthetic, you will be asked to follow fasting instructions. This means not eating or drinking, typically for about six hours before a general anaesthetic. However, it’s important to follow your anaesthetist’s advice.
At the hospital, the nurse may check your heart rate and blood pressure, test your urine and blood, and arrange for x-rays of your knee and/or chest also to check your general health.
Your surgeon will discuss with you what will happen before, during and after your procedure, and any pain you might experience. This is your opportunity to understand what will happen, and you can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead, which you may be asked to do by signing a consent form.
You may also be asked to give your consent to have your name on the National Joint Replacement Register, which is used to follow up the safety, durability and effectiveness of joint replacements and implants.
You may be asked to wear a compression stocking on the unaffected leg to help prevent blood clots forming in your veins (deep vein thrombosis, DVT ) during the operation. You may need to have an injection of an anti-clotting medicine called heparin as well as, or instead of, stockings.
A knee replacement usually takes between two to four hours.
Your surgeon will make a single cut (10 to 30 cm long) down the front of your knee, and will move your kneecap to one side to reach the knee joint. They will remove the worn or damaged surfaces from both the end of your thigh bone and the top of your shin bone. At this point the anterior cruciate ligament (ACL) is usually removed and sometimes the posterior cruciate ligament (PCL).
For support, your surgeon won’t remove your collateral ligaments. He or she will shape the surfaces of your thigh and shin bones to fit the artificial knee joint and then fit the new joint over both bones.
Sometimes the back of your kneecap is replaced with a plastic part. This is called patellar resurfacing.
After your surgeon has fitted the new joint, the wound is closed with stitches or clips and covered with a dressing. Your surgeon will tightly bandage your knee to help minimise swelling.
You will need to rest until the effects of the anaesthetic have passed. You may not be able to feel or move your legs for several hours after an epidural anaesthetic.
You may need pain relief to help with any discomfort as the anaesthetic wears off.
For the first day or so, you may have an intermittent compression pump attached to special pads on your lower legs. By inflating the pads, the pump encourages healthy blood flow and helps to prevent DVT. You may also have a compression stocking on your unaffected leg. This helps to maintain circulation.
A physiotherapist (a specialist in movement and mobility) will usually guide you daily through exercises to help your recovery.
You will be in hospital until you can walk safely with the aid of sticks or crutches. When you’re ready to go home, you will need to arrange for someone to drive you.
Your nurse will give you some advice about caring for your knee and a date for a follow-up appointment before you go home.
The length of time your dissolvable stitches will take to disappear depends on what type you have. However, for this procedure they should usually disappear in about 6 weeks. Non-dissolvable stitches and clips are removed 10 to 14 days after surgery.
If you need them, you can take over-the-counter painkillers such as paracetamol or ibuprofen. Always follow the instructions on the accompanying consumer medicines information leaflet and if you have any questions, ask your doctor or pharmacist for advice.
The physiotherapy exercises are a crucial part of your recovery, so it's essential that you continue to do them for at least two months.
You will be able to move around your home and manage stairs. You will find some routine daily activities, such as shopping, difficult for a few weeks. You may need to use a walking stick or crutches for up to six weeks.
You may be asked to wear compression stockings for several weeks at home and you will probably need to take anti-clotting medicine for a month or so after surgery, which will be started while you are in hospital. It is important to take the full prescribed treatment course as blood clots may form if they are stopped too early. When you’re resting, raise and support your leg and knee with some padding under the natural hollows of the body to help prevent swelling in your leg and ankle.
Depending on the type of work you do, you can usually return to work after 6 to 12 weeks.
Follow your surgeon's advice about driving. Don’t drive until you are confident that you can perform an emergency stop without discomfort.
Knee replacement surgery is commonly performed and generally safe. However, in order to make an informed decision and give your consent, you need to be aware of the possible side effects and the risk of complications of this procedure.
Side effects are the unwanted but mostly temporary effects that you may experience after having a procedure, for example feeling sick as a result of the general anaesthetic. The main side effects associated with knee replacement surgery are:
This is when problems occur during or after the operation. Most people are not affected. The possible complications of any operation include an unexpected reaction to the anaesthetic, excessive bleeding or developing a blood clot, usually in a vein in the leg (DVT).
Specific complications of knee replacement are uncommon, but can include those listed below.
The artificial knee joint usually lasts for up to 15 years, after which you may need to have it replaced.
The exact risks will differ for every person, so we haven’t included specific details here. Ask your surgeon to explain how these risks apply to you and about the general risks of surgery.
Australian Orthopaedic Association
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Last published: 31 March 2012
Tags: knee surgery, knee replacement, bones and joints,
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