Unlike a total knee replacement, where all the joint surfaces are replaced, the uni-compartmental knee replacement only resurfaces the part of the joint that involves the inner side of the knee. It is now a routine operation with reliable results. The type of replacement we use was designed in Oxford, UK.
The inner part of the joint is replaced when it is causing a lot of pain due to wear and tear. If the remainder of the joint is not worn then it can be left alone. The advantages of this type of replacement, compared to a total knee replacement, are that you would mobilise more quickly afterwards and would retain a better range of movement in your knee. The scar is smaller and you should be able to leave hospital sooner. It is only performed when alternative treatments have failed or are not appropriate. Your surgeon can discuss this further with you if necessary.
You will be seen about 1 - 2 weeks before your operation in the pre-operative assessment clinic. This is to ensure that you are medically fit enough to have it performed and for infection screening. You will be admitted to the ward either on the day of your operation or occasionally on the day before. You will be seen again on the ward before going to the operating theatre. The procedure will be explained again and the consent forms will be signed. The final details will be checked and the knee being operated on will be marked.
Knee replacements are usually performed under a spinal or epidural anaesthetic, which makes the legs numb. You would not necessarily be asleep, however, you can be given something to make you sleepy if you wish. Not everyone is suitable for a spinal anaesthetic and a general anaesthetic would be used instead, where you would be asleep. Your anaesthetist will decide on the safest and most appropriate option for you when they see you, usually the day before or on the morning of your operation.
A cut about 10 cms long is made in front of the knee. The damaged joint surfaces are inspected. If it is found that the other parts of the joint are worn or there is ligament damage then you would not be suitable for the Oxford uni-compartmental replacement. In this case it would be converted to a total knee replacement (see separate Information Leaflet), this final decision is only made at the operation. Following this the worn joint surfaces are removed. They are replaced by a new surface of metal on the end of the thighbone and top of the shinbone, with a mobile plastic spacer between the two. The new surfaces are cemented in place. The operation usually takes between one and two hours. A drain is sometimes put into the knee, which is removed the next day. A blood transfusion is hardly ever needed and may be taken from the knee drain bag (depending on the drain type). Alternatively, we use blood from the blood bank, which we try to avoid if possible.
You should go home between 2 - 5 days after your operation.
When you return from theatre you will have a light bandage in place. Any discomfort you feel will be relieved with painkillers as necessary. This may be by a self-administered system (PCA pump), which the anaesthetist will explain to you, or by injections/tablets. Whichever is used your pain will be better controlled if something is given just before the pain comes on, rather than when it is established.
Yes. Physiotherapy is very important. The physiotherapists will get you up and walking and bending the knee the day after your operation. You will get a much better result from your new knee if you do the exercises the physiotherapists show you. You may need to continue attending the physiotherapy department for a few weeks after your operation.
Yes. Your surgeon will see you regularly after your operation on the ward. You will be seen again 6 weeks after discharge to assess your progress.
In the long term (after 1 year) you will not need to come to hospital for follow up unless there are any problems. However, we are keen to find out how our patients are progressing. You may therefore be contacted to complete a postal questionnaire some time after your operation (usually every 5 years). We may also invite you to attend for an X-ray at a time that is convenient for you. Any information returned would be handled sensitively and confidentially, it may be stored on a secure computer register.
It is possible that the National Joint Registry, which holds details of all the joint replacements performed in the UK, may also contact you. You would only be contacted by them if you have consented to do so prior to your operation. This will be discussed at the pre-assessment clinic.
This depends on your job and your general health, but most patients return to work between 4 and 8 weeks after their operation.
Although there are no "rules" it is generally thought unsafe to drive for 6 weeks after knee replacement, though you can travel as a passenger in a car when you feel up to it. You are advised to contact your car insurance company before you start to drive again.
You should retain a good range of movement in your knee after operation, so kneeling should be possible if you can do it comfortably.
An artificial knee joint is not a normal knee and you have to look after it to some extent. You should have no difficulty with walking, cycling, swimming or golf. Light running may also be possible. Sports that risk serious injury to the knee such as skiing are also not recommended! You can discuss other sports with your surgeon.
You should be able to go away within the UK following discharge from hospital, providing any long journey is appropriately broken. Flying immediately after lower limb surgery is associated with an increased risk of deep vein thrombosis (see below). Although no fixed guidelines exist we recommend that you should not fly for 3 months following a knee replacement.
We can never guarantee the result of any operation. Most people are delighted with the results following knee replacement, especially where pain was the main symptom before operation. However, the replacement will not give you a knee like it was when you were younger. So occasional aches and clicks are normal following replacement.
For most people we estimate a replacement knee will last 10 to 15 years.
If the replacement does become worn or loose then it can be removed and another replacement inserted. This is a much bigger operation than the first replacement but is usually successful. The same procedure would be performed if the remaining non-replaced joint parts became worn. Remember that knee replacement is successful and working well in over 95% of patients 10 years after the operation.
The majority of people have a knee replacement without having any problems. A few have minor difficulties or complications, which are usually easily dealt with. Nearly all patients will notice a patch of numbness to the outer side of the scar. This gradually gets smaller and is not troublesome. Rarely more serious complications can occur, which you should be aware of and bear in mind when deciding whether to have your replacement performed.
Anaesthetic: Problems can occur related to your general health and the anaesthetic. The majority of potential problems will be picked up at the pre-assessment clinic. Your anaesthetist will be able to discuss this further with you.
Bleeding: It is not unusual for a little bleeding to occur into the bandage and this should not cause concern. Rarely more severe bleeding occurs into the knee making it swollen and uncomfortable, this usually settles with time.
Urinary retention: Some patients find it difficult to pass urine after the operation. A tube (catheter) may need to be passed into the bladder for a day or two. This is more common for men.
Swelling: Some swelling of the knee after surgery is inevitable and is treated by compression, ice and elevation. It is important to keep the knee moving even if it does swell.
Stiffness: Physiotherapy and home exercise are important in achieving a mobile and strong knee. Nevertheless, some patients develop a very stiff knee that will not respond to this. Your surgeon may decide that you should have the knee manipulated under a short anaesthetic to improve the movement. This degree of stiffness is very unusual after uni-compartmental knee replacement.
Pain: Some discomfort is felt after the operation but should pass off. A small number of patients still have pain months later. If this happens it will be investigated and any cause treated. Usually, no cause can be found.
Deep vein thrombosis: This can occur to any one under going lower limb surgery. The risk is greater if you have had one before or you are on hormone replacement therapy (which should be stopped 6 weeks before operation). They rarely cause direct problems, but can potentially be serious because of the risk of spread to the lungs (pulmonary embolism). Treatment usually involves taking warfarin (to make the blood clot less easily) for a 3 month period.
Infection: A little redness around the wound due is not uncommon and, occasionally, is caused by infection that is treated with a short course of antibiotics. Even though great care is taken deep infection around the new joint occurs in 1 in 100 replacements. This is difficult to treat and may require further extensive surgery.
Wear and loosening: Your knee replacement may eventually wear out or become loose. It may begin to swell, feel uncomfortable and unstable. If this happens you should ask your GP to refer you back to your surgeon.
Dislocation: The plastic spacer between the metal replacement surfaces is not fixed into place, which is why you would retain your knee mobility. However, it can rarely come out of place (dislocate). This usually happens if the knee is fully bent and twisted. If this occurs it may be put back in by manipulation or a small open operation.
Following discharge you should contact your GP who will assess your knee and take appropriate action depending on the problem.
If you still have any questions please ask your surgeon.