Partial Knee Replacement

The knee joint is made up of three bones, these are, the femur (thighbone), the tibia (shinbone), and the patella (kneecap). The knee is a hinge joint, however, it has a complex rotational component that occurs with flexion and extension of the knee. The knee is held together by muscles, ligaments and other soft tissue, that enables it to bear a significant weight. Cartilage is located inside the knee joint and provides shock absorption during weight bearing activities (such as walking or climbing stairs).

As we get older the cartilage in our joints becomes more brittle and is likely to wear out or degenerate. This can lead to osteoarthritis, which is the wearing out of the lining (articular) cartilage, and is the most common cause for a total knee replacement. Due to the osteoarthritis, the cartilage in the knee breaks down and the result is a badly damaged joint surface, often, with bone rubbing on bone. This can become stiff and may become deformed or angulated. In the early stages of arthritis, pain is normally mild and only felt after exercise. It is usually a dull ache and may be associated with some swelling. As arthritis progresses the pain will become constant and more severe. It may be painful at rest and wake you up at night.

If you have arthritis in your knee, the first step is to try simple treatments such as taking painkillers and anti-inflammatories, gentle knee exercises and maybe walking with a stick. Weight loss can also significantly improve symptoms. Used in combination, these treatments can improve your pain and level of function significantly and you may not need anything else at this stage.

If you have tried all of the above, and you are still getting significant pain and stiffness that is preventing you from doing the things you want to do or you are not able to sleep because of the pain, a total knee replacement may be the best solution for you. The main reasons for knee replacement surgery are:

• Pain relief
• Improve stability
• Improve alignment and correct bone deformity (bow leg or knock knees)
• Improve quality of life

Often arthritis affects one part of the knee more than the rest. The knee can be thought of as 3 ‘compartments’ combined: the medial compartment (inside of the leg), the lateral compartment (outside of the leg) and the patellofemoral compartment (at the front behind the kneecap). Partial knee replacement replaces only the worn out compartment of the knee, and leaves the rest of the knee, and the cruciate ligaments (ACL and PCL) intact. It is also called Unicompartmental Knee Replacement (UKR).

There are two main advantages of partial knee replacement over total knee replacement.

Firstly, it is a smaller operation. This means that the risk of complication is lower: less bleeding, fewer blood clots, less stiffness, smaller wound, fewer infections. Also, it means that the recovery is quicker.

Secondly, because the ligaments are left intact, the knee moves more like a normal knee after surgery. In a total knee replacement, we need to remove the ACL, and sometimes the PCL; this means the way the knee moves afterward is always a bit different from a normal knee. This is why it can be harder to get back to sports and more demanding activities after knee replacement.

It is rare for the other areas of the knee to develop arthritis later. Usually if the rest of the knee is going to develop arthritis, it will be showing signs of arthritis in the first place and we will do a total knee replacement. If there is bone on bone arthritis in the medial compartment and the lateral compartment has minimal arthritis, then the chance of it developing down the track is less than 5%. If it does develop, and the symptoms are bad enough, then we can either replace the lateral compartment too, or revise the partial replacement to a total knee replacement.

The main disadvantage is the small possibility that arthritis will develop in the other compartments. Overall, partial knee replacements are more likely to need further surgery or revision than total knee replacements. Another reason for this is that inexperienced surgeons find partial knee replacement a difficult operation and have higher complication rates. However, surgeons who have had extra fellowship training in partial knee replacements, and do more of them, have a low revision rate. The revision rates of the Melbourne Hip and Knee surgeons are very low.

Robotic arms or computer controlled burrs can be used to help in partial knee replacement. This is an exciting development. We hope that in the future it will mean that partial knee replacements will perform even better than they currently are. Melbourne Hip and Knee surgeons have trained in and are using both the MAKO™ and Navio™ robotic systems.

Our results with conventional partial knee replacements have been excellent, and because the non-robotic partial knee replacement has a 30-year track record, we are using robotic surgery for some, but not all, of our partial knee replacements.

Once you and your surgeon have decided to proceed with surgery, there are several steps to be taken to ensure your procedure goes smoothly.

• Physician review: Joint replacement surgery is a fairly big operation and the anaesthetic for this is a stress on the body. There is always a small chance of heart attack or stroke with this anaesthetic. While you may have had a check-up or some blood tests by your GP we think your health is worth a more careful check. As a routine we organise an appointment with a specialist physician. This specialist will have a careful listen to your heart and lungs, review your blood tests and ECG and discuss your health and hospital care with you. If you are on any medication they may want to stop this or change it prior to your surgery especially if you take blood thinning medication (eg warfarin or Plavix). It is important that the physician you see prior to your operation works at the hospital where you are having the operation. They will then help with your care and if there are any problems after the operation someone who has seen you before and knows you will be there to give you the best possible care.
• Pre-Admission Clinic: Most hospitals run a specific joint replacement preadmission clinic to help patients prepare for their hospital admission. These sessions include presentations from nurses, physiotherapists and occupational therapists. It is strongly recommended that you attend one of these clinics.
• Start pre-operative exercises: It is important to be as flexible and strong as possible before undergoing a total knee replacement. Many patients with arthritis favour the pain free leg, as a result muscles can become weaker, making recovery slower and more difficult. It is important therefore, to begin an exercise program before surgery to learn and practice the exercises that will improve your strength and flexibility making recovery easier and faster. Melbourne Hip and Knee offers pre and post-operative physiotherapy sessions onsite at our main rooms in Hawthorn East. To book an appointment call 9882 7753, alternatively, if you have a regular physiotherapist they will be able to get you on track.
• Make arrangements for help around the house: It is important to have your house ready for when you return home. You may need to modify sleeping arrangements if they are up a lot of stairs. You should also put things that you use often within easy reach, remove cords or obstructions from walkways, arrange for someone to walk the dog and collect the mail.
• Stop smoking: Stop smoking as long as possible prior to surgery. Smoking delays your healing process. It reduces the size of your blood vessels and decreases the amount of oxygen circulated in your blood. Smoking greatly increases your chances of getting an infection of your prosthesis or the wound breaking down. Smoking can also increase clotting, which can cause problems with your heart. Smoking increases your blood pressure and your heart rate. If you quit smoking before you have surgery, you will increase your ability to heal.

• Arrival: You will be asked to attend the hospital approximately two hours before the anticipated time of your operation. There are several stages to your admission process and this ensures that adequate time is available.
• Fasting: Fasting is important to ensure your procedure can occur, and it includes refraining from all food and fluids, including water, chewing gum, mints or lollies. You will be asked to fast for at least six hours before your surgery
• Medications: Please bring all current medications with you to the hospital. Please check with your surgeon to determine if you should take your regular medications on the day of surgery.
• X-rays/Scans/Imaging: please bring all that you have to the hospital. This includes the actual scans (not just the reports).
• Luggage: space is limited so avoid bringing unnecessary items. We strongly recommend you do not take valuables to hospital, no liability for loss, theft or damage of valuables will be accepted by hospitals.

The following processes will occur:

• Clerical admission - you will be initially admitted by a clerical staff member at the hospital. They will check all of your administrative details and take any payments due.
• Clinical admission - you will then undergo a clinical admission where a nurse will discuss your medical history, this may include recording your height, weight and blood pressure. If any blood tests or other investigations are required they will be taken at this time. You will be changed into a theatre gown.
• Anaesthetic review - your anaesthetist will visit you prior to your surgery to explain the type of anaesthetic you will be receiving.
• Surgeon – your surgeon will again explain the procedure you are about to undergo. They will mark the correct part of your body where the procedure will happen. You will also sign surgical consent.

• Recovery
  When you wake you will be in the recovery room with intravenous drips in your arm, and a number of other monitors to check your vital observations. You may have a button to press for pain medication. Once stable, you will be taken to the ward. The post-operative protocol is surgeon dependant. You will start moving your knee and walking on it within a day of surgery. You are encouraged to begin physiotherapy exercises straight away and to bend and straighten the knee to help regain muscle strength.
   
• Dressings
  You will initially have a large outer bandage on your knee. This will usually be removed about 24 hours after your operation. There will be a smaller waterproof dressing beneath this which should remain in place for two weeks. Dissolvable stitches are used.
   
• Going Home
  Normally you would be in hospital for two to three days. Staying in a rehabilitation hospital is usually not required after partial knee replacement, however, if you feel unsafe walking, or if you don’t have people to help at home then you can be transferred to a rehabilitation hospital for 1-2 weeks where physiotherapists will work more closely with you. You will be discharged on a walker or crutches and usually progress to a cane at six weeks. Please ensure you arrange for someone to pick you up.
   
• Pain Management
  You should take regular painkillers and ice the knee regularly for the first few weeks to make sure the knee feels comfortable, and also to allow you to do your physiotherapy exercises. You should wear compression stockings (day and night) and take daily blood thinners for one month after surgery to decrease the risk of developing blood clots. It takes several weeks for the pain to settle down and it can be several months before it really feels normal.
   
• Post-operative appointment
  You will usually have a post-operative appointment booked to see your surgeon approximately two weeks after surgery. Your appointment information is on your admission letter. Please call Melbourne Hip and Knee if you are unable to locate this information. If you are still in a rehabilitation facility when you are due to have your appointment, please call us to reschedule.

You will have physiotherapy each day in hospital and you should continue to see a physiotherapist after you leave hospital. If you have seen a physiotherapist prior to surgery you should return to them after the surgery for follow up exercises.

How quickly you return to activity is highly variable. In general, younger and more active patients are able to return to activity quicker. If you have preoperative physiotherapy this will aid your quicker return to activity after your surgery.

Driving. If you have your left knee replaced and you drive an automatic car then you can drive when you are off all strong painkillers and can easily get in and out of the car. This may be as soon as 3 weeks after your operation. If you have your left knee replaced and you drive a manual car it will often take 5-6 weeks for the knee to be strong enough to drive.
If you have your right knee replaced, then it needs to be strong enough and move well enough to quickly change pedals and push hard on the brake. This will often take 6 weeks or longer.

Work. If you have a desk job and you can get to and from work you may be able to return to work as early as 3 weeks after surgery although it often takes 6 weeks. If you return before six weeks, you may need shorter hours or fewer days. You can work from home as soon as you are off strong pain killers. For patients who perform more physical work you may have to stay on light (restricted) duties for a couple of months.

Walking unaided. After a few weeks you may be able to walk around the house unaided but many people continue to carry a walking stick or crutch for a few more weeks when outside the house for support, balance and to warn the general public that you need more space.

Sport (swimming/hydrotherapy). You can start hydrotherapy as soon as the wound has fully healed, this is normally around 3 weeks after surgery but make sure you get the clearance from your surgeon first. As part of your rehabilitation you may start on an exercise bike within a few weeks. It will normally take a couple more weeks before you are able to ride a normal bike. Returning to sport such as golf and doubles tennis will take at least 4 months and may not be possible for all patients

Sex. Once your wound has healed and you are comfortable you are able to return to sexual activity. Positions where you are resting on the knee or have the knee bent a lot may be difficult.

Partial knee replacement is designed to last you the rest of your life. However, there is a chance it can wear out, become loose, or need further surgery. In the past some people have thought of it as a temporary procedure until you need total knee replacement, but this is not the case. Studies following patients who have partial knee replacements with experienced surgeons show that 15 years after surgery about 10% will have needed to be revised. Studies following patients with less experienced surgeons show a much higher rate of revision.

• Anaesthetic
  There are risks associated with the anaesthetic, including the possibility of heart attacks, strokes and breathing difficulties. The chance of these occurring is generally very low and this is why you are fully assessed by a physician before you have your operation to see if there is anything that needs to be done to decrease this risk further.

• Infection
  There is a risk of the knee replacement getting infected. This occurs in 1 in 100 operations. If the knee replacement gets infected, you may need further operations to wash it out. If the infection is severe, the whole knee replacement may need to be removed and then replaced again once the infection is cured.

• Nerve Injury
  There is a small risk of injury to the nerves and blood vessels around the knee. The chance of any major injury is extremely low. You will, however, always develop a patch of numbness on the outer side of the knee which will be permanent to a degree. This is because one of the nerves that provides feeling to that part of the knee always gets cut when the skin is incised.

• Blood Loss
  If you lose a lot of blood from the operation, you may require a blood transfusion.

• Blood Clots (DVT)
  As mentioned above, there is a risk of developing clots in the legs which can then go to the lungs. You will be given special stockings to wear and blood thinning medication to reduce this risk. It is also important to do you exercises to increase blood flow to the lower leg.
  Pain. While the aim of surgery is to improve your pain some patients report that the knee is still a little bit stiff and uncomfortable after the surgery. The knee will not bend as well as a knee that has never had any problems and may always feel a little unnatural.

It is uncommon to need a blood transfusion after joint replacement surgery but some patients for religious or personal reasons never want to have a transfusion.

If this is the case our surgeons are happy to discuss ways to fulfill your request. We will ensure you have an adequate blood count prior to surgery and various medication and techniques can be used to preserve blood during your operation.

If you have any further questions, please ask you surgeon.