Partial Knee Replacement Surgery

Partial Knee Replacement Surgery, also commonly referred to as, Unicondylar Replacement Surgery, or Knee resurfacing is a surgical procedure which involves the resurfacing of the worn out bony surface of the knee joint.

In a Partial Knee Replacement procedure either the the inside joint (medial); outside parts of the knee (lateral); or area between the knee cap and the upper front surface of the femur (patellofemoral) is replaced. This means only the damaged part of the knee cartilage is replaced with a prosthesis not all parts as in Total Knee Replacement Surgery.

    1. Who is suitable for Partial Knee Replacement surgery?
    2. What are the advantages of the procedure?
    3. What Implants are used?
    4. How is a Partial Knee Replacement procedure performed?
    5. What happens after surgery?
    6. How is the pain managed?
    7. What precautions should I take at home?
    8. What complications and risk are there?
    9. Estimate of Fees

1Who is suitable for Partial Knee Replacement surgery?

Compared to total knee replacement surgery, partial knee replacement surgery better preserves range of motion and knee function because it preserves healthy tissue and bone in the knee. For these reasons patients tend to be more satisfied with partial knee replacements compared with total knee replacements and they are still candidates for total knee replacement should they ever need it in the future.

Patients with medial, lateral, or patellofemoral knee osteoarthritis can be considered for a partial knee replacement. “Medial” refers to the inside compartment of the joint which is the compartment nearest the opposite knee, while “lateral” refers to the outside compartment farthest from the opposite knee. Medial knee osteoarthritis is commonly caused by damage to knee cartilages known as the menisci.

Patellofemoral osteoarthritis is osteoarthritis of the joint between the kneecap (patella) and the lower leg bone (tibia). This type of knee osteoarthritis is more common than lateral compartment knee osteoarthritis.

Professor Kohan will ask you to identify the area of pain in your knee then check your range of motion and the knee’s stability. An X-ray of the knee will determine your eligibility for partial knee replacement surgery.

To be a candidate you must have an intact anterior cruciate ligament, a sufficient range of knee motion, limited inflammation, minimal pain at rest, damage to only one compartment, and no calcification of cartilage or knee dislocation.

Further testing may be required if the diagnosis is not clear:

  • X-Ray – this needs to be weight bearing. The use of a weight-bearing x-ray can determine the extent of the degeneration in the joint.
  • Blood Test – This may determine if there is inflammatory arthritis or infection in the hip.
  • Scanning and MRI can determine if you have avascular necrosis.
  • Bone Mineral Density determines the condition of the bone or the presence of osteoporosis.
  • Arthroscopy

If your knee pain persists despite anti-inflammatory medications and maintaining a healthy weight you may want to consider a partial knee replacement.

2What are the advantages of the procedure?

Partial Knee replacement is considered ‘retread’ surgery. This means the diseased bone is resurfaced only, leaving the rest of the joint untouched. The device is small consisting of metal and plastic components and the operation itself is less invasive.

The main advantages of a successful partial knee replacement procedure are:

    • Smaller Incision: The incision itself is approximately 10cms long.
    • Less Blood Loss: artial knee replacement surgery is considered minimally invasive surgery and eliminates the need for blood transfusion.
    • Less Bone Removed.: Partial knee replacement surgery means ‘retreading’ the bone with metal on plastic. Therefore, only a small amount of bone needs to be removed, approximately 3 – 4mm, to fit the device. Total knee replacement requires the loss of approximately 10mm from all compartments.
    • Lower Morbidity: Partial knee replacement surgery greatly reduces the disruption to the joints, providing a shorter recovery period and a decrease in complications.
    • Shorter Recovery Time: Most Partial knee replacement patients are walking 2 – 3 hours after surgery. Total time spent in hospital approximately 6 – 8 hours & within 2 weeks patients are back driving, playing golf, or resuming normal activities

3What Implants are used?

A partial knee replacement implant is much smaller than a total knee replacement implant and does not disturb the healthy tissues of your knee. Most implants are metal-on-plastic and resurfaced with a cobalt chrome implant that conforms precisely to the anatomy of the knee. The tibial component would be made of polyethylene and only require minimal bone removal to secure the implant.

If only a single compartment in your knee is to be replaced, Professor Kohan will use a unicondylar (UNI) fixed bearing knee implant, the most commonly used prosthesis, or a unicondylar mobile bearing knee implant. The advantage of these types of implants are such that only the arthritic portion of your knee to be covered by the implant needs to be removed.

In joints with mobile bearings, the plastic spacer isn’t fixed but allowed to move back and forth with the action of the joint. Many believe that this allows greater freedom of movement in the joint and also reduces the amount of wear that could take place. Traditional partial knee replacements however retain good movement even in joints with fixed bearings and demonstrate a limited history of wear.

If osteoarthritis has progressed to more than one compartment of your knee we now have the ability to remove two (bicompartmental) or even three (tricompartmental) components of your knee joint and replace them with partial knee implants.

The advantage of a partial knee replacement rather than a total knee replacement is less damage to healthy ligaments during the procedure and the likelihood that your repaired knee will function and feel more like your natural knee.

4How is a Partial Knee Replacement procedure performed?

Partial Knee Replacement surgery requires resurfacing of the damaged surfaces of the knee joint. A partial artificial knee joint is designed to fit over the edges of the damaged joint and to replace the damaged areas with one that can be used pain free.

The procedure is usually performed on an outpatient basis (no overnight hospital stay required).  Discharge from hospital (as long as you feel well enough) will be  4 – 6 hours after surgery.

The operation will take approximately 1.5hrs plus approximately 45 minutes to an hour in recovery. You will be out of bed and walking 2 – 3 hours after surgery.

The incision is approximately 10cms and is made down the middle of your knee over the top of your kneecap. The scar line may not be completely flat immediately after surgery but will settle down after a few weeks. A tourniquet is placed around your thigh during surgery; this may cause bruising from your thigh down into your foot.

When you wake up, you will have a drain in your knee. This will be removed before you go home. A knee brace will be in place for 48 hours after your operation.

The operation will be performed under general anesthesia. Dr D Kerr will discuss the anesthetic and pain control with you. It is important you make an appointment to see Dr Kerr approximately 1 week prior to your operation.

There are two main techniques in partial Knee replacement surgery; the Repicci Method and the Oxford Method.

The Repicci Method

The Oxford Method

5What happens after surgery?

Immediately after surgery, you will wake up in the recovery room. You may feel a bit groggy. Professor Kohan and his staff will monitor you, checking your blood pressure, temperature and pulse. Dr Kerr will also assess your pain level. Post-operative x-rays will be performed in recovery.

After 45 minutes – 1 hour you will then be transferred back to your room on the ward.

When you arrive to your room, you will have:

  • A compression garment around the operation site to apply pressure there. This is removed 24 hrs after surgery.
  • A pain catheter which will be removed before discharge. We inject local anaesthetic through this to maintain the pain relief.
  • TED Stockings (knee high white stockings) on your legs which must be worn for 2 weeks post procedure.
  • A drip in your arm. This will provide hydration and blood if you need it

In the first week following surgery you may experience:

        • Swelling – From your thigh down into your foot is common. This at times may be quite marked. The swelling will increase for the first few days after surgery and will gradually diminish. Some swelling can be present for 12 months or so. The swelling may be diminished by walking as the muscle function will push the fluid away. When you stop walking, the limb should be elevated above the level of the hip.
        • Bruising – Marked bruising can be found in some patients. This can be found from your thigh down into your foot. At times the bruising can be quite dramatic but it will resolve. It is the result of some residual bleeding making its way to the surface. The body will eventually remove the bruising. It is also the result of the blood thinning tablets you will be taking.The blood thinning tablets will tend to make the bleeding after surgery a little more marked because the blood clotting is impaired. This is however preferable to developing a blood clot.
        • Blistering – On occasions blisters will develop near the operation and possibly above it. The blistering is due to surface fluid. It looks dramatic but it is of no consequence and always resolves. One cause may be the bandage rubbing on the skin. Sometimes, when the blood dries in the bandage it can be like cardboard and rub on the skin producing these blisters. We change the bandage after about a week but would prefer not to interfere with that earlier because of the risk of infection. After about a week the wound is sealed enough to be a reasonable barrier against infection. Another cause for the blistering is tissue swelling. This is associated with the bruising and is a result of fluid leaking into the skin. These blisters always go away. They may burst and leak fluid and again the appearance may be dramatic. Sometimes if they are large we may burst them. This is so that the dressings sit more comfortably.
        • Muscle soreness – Your muscles can feel stiff and sore to touch. During the operation some stretching and pulling of the muscles occurs. This may result in some pain like a corked thigh. Occasionally you may feel cramps and spasms. The discomfort however will resolve and activity such as walking, stretching, physiotherapy, etc, will help to speed the improvement.
        • Heat – The operated site may feel hot and the heat may last for 12 months. As part of the healing process the operation site requires more blood supply from the body and it is this extra blood supply which is the cause of the local heat.

For the first 2 weeks after surgery your activity level is usually limited however you will be able to walk independently, use the bathroom and perform normal activities of daily living. It is important however, to keep on trying to use the knee as normally as possible.

After 6 weeks you will be able to engage in moderate activities, i.e. driving a car and climbing stairs.

Within 8 weeks you will have resumed most of your normal activities. Complete surgical healing takes 6 – 8 weeks but sometimes longer if the arthritis was very severe or the knee very deformed. During this time some swelling and discomfort is normal and should be manageable with the prescribed medication.

6How is my pain managed?

Post-operative pain is one of the major outcomes of surgery and relief of the patient’s distress is an important goal in its own right. Severe pain often leaves the patient permanently scarred and terrified of even minor surgery.

Meticulous pain management is pivotal in achieving acute rehabilitation.

Our objectives are:

  • No pain or low levels of discomfort for the entire peri-operative and convalescent period.
  • Side effects limited or reduced to negligible levels.
  • Acute rehabilitation and early discharge.

The Joint Orthopaedic Centre have developed a multimodal technique for the control of pain following knee and hip surgery, called The Kohan-Kerr “Local Infiltration Analgesia Technique” (LIA).

LIA is based on systematic infiltration of a mixture of ropivacaine, ketorolac, and adrenaline into the tissues around the surgical field to achieve satisfactory pain control with little physiological disturbance.

The technique allows virtually immediate mobilization and earlier discharge from hospital. It places meticulous pain management at the centre of immediate post-operative care and it is central to achieving our stated goals.

LIA adopts three pathways:

    • The first pathway, involves the establishment of an effective local anaesthetic block at the time of the operation (The LIA Kohan-Kerr Technique). In essence, we try and numb all the parts which have been operated on and which may generate pain. After the operation the area involved usually feels numb. This is a feeling similar to that experienced at the dentist when a local anaesthetic injection is given
    • The second pathway involves oral medications such as Panadine Forte and Nurofen. These are prescribed to try and improve the pain control.

Please note: Panadeine Forte may cause nausea if the dose is too high. If you start to feel nausea, halve the dose of this medication. It can also causes constipation. To help prevent constipation, you should drink plenty of water, and take fiber containing stool softener, such as Metamuseal/Normacol night and morning.

Pain medications can be reduced after 3 days. Stop the Panadeine Forte first, and then reduce the Neurofen tablets to 2 every 6 hours as the pain subsides.

  • Postoperatively, a pain controlling skin patch may be applied, which also contains a slow release analgesic

We have found this process to be extremely effective at controlling pain. We cannot say that you will have no pain, but rather, that manageable discomfort will be present. We aim for the discomfort not to reach a level, which would interfere with your ability to mobilise effectively.

7What precautions should I take at home?

Precautions to take following Knee Surgery:

            • Avoid chairs that are low.
            • Avoid slippery surfaces.
            • Avoid twisting your knee for 6-8 weeks after surgery.
            • Avoid siting in the same position for long periods. 45 minutes at a time should be enough. Sitting for long periods increases the likelihood of stiffness.

Incision Care

The incision is sutured with skin staples which will be removed 10-12 days after surgery. You will have a firm bandage from your foot to your thigh following surgery which is usually removed on day 5 at your first post op appointment.

The nurses in the hospital will help you change the dressing if needed before you leave the hospital.

You must not get the incision wet until the staples are removed – a sponge bath instead of a shower is therefore recommended for 5 days post surgery.

You may shower after the sutures are removed but may not bathe or swim for 2 more weeks after that.

Your second post-op appointment is to remove the skin clips from your wound. Some swelling and warmth on and around the incision area is expected. If you develop increased redness, drainage or a fever please call the office immediately.

Bruising around the thigh area is also common. It may extend down into your ankle and should resolve in 10 – 14 days.

You may apply Vitamin E or some moisturising lotion on and around the incision area after the staples have been removed.


Each individual has his/her own set of expectations. Each patient is treated as an individual with general health, age and attitude considered.

An important thing to remember is that you are not sick. You have a problem with your knee that needs to be fixed.

Getting back on your feet after surgery is the most important goal. ‘Motion is Lotion.

For the first 2 weeks after surgery your activity level is usually limited however you will be able to walk independently, use the bathroom and perform normal activities of daily living. It is important however, to keep on trying to use the knee as normally as possible.

After 6 weeks you should be able to engage in moderate activities, i.e. driving a car and climbing stairs.

Complete surgical healing takes 6 – 8 weeks but sometimes longer if the arthritis was very severe or the knee very deformed. During this time some swelling and discomfort is normal and should be manageable with the prescribed medication.

The most important thing is to have a positive attitude!

Physiotherapy & Exercise

Gentle exercises help strengthen the muscles around your new knee and regain your knees range of motion.

As soon as possible your physiotherapist helps you start walking a few steps at a time to promote healing. As you progress from crutches and then to a cane you may feel somewhat off balance at first. Gait training helps you regain confidence and your normal walking motion before going home.

Results of a knee replacement are classified as excellent if activities of daily living can be performed without pain or restrictions. (This does not include running sports). Results are classified as good if occasional mild pain occurs and only slight restrictions of movement are present.

For the past 5 years studies have usually recorded 95% good to excellent results.

Your prosthetic knee can wear out or loosen and may require replacement if necessary. On the other hand, people live longer now and you may out-live your new knee. Regular review is recommended.

In order to reduce stiffness and obtain maximum function of your knee it is important to maintain a good balance of rest and exercise. Listen to your body, too much activity will produce increased swelling, and/or pain, too little will prolong your recovery, and/or limit your knee mobility.

To promote circulation, remember to do your ankle, foot stretching exercises regularly.

On the second day post surgery, remove the knee brace and begin moving the knee and walk, as your knee will allow. The fourth day after surgery you may begin your leg exercises.

Knee Stretching:
Sit in a chair so that your bottom is at the back of the chair; place your feet on a phone book.

Cross your legs at the ankles (good one over the operated leg). Push back leg with front leg until stretch is felt and hold for 15 seconds.


Raise foot of operated leg, straightening it out and hold it for 15 seconds. Repeat 15 times.


Do these exercises 3 – 4 times a day. Continue doing these exercises until you return to your normal activities.

8What complications and risks are there?

As with all surgery there are certain risks and potential complications. Although the incidence of these risk factors is low each patient needs to be informed of the possible complications prior to surgery:


Infection is uncommon occurring in less than two percent of operations. It is usual for each patient to be is given intravenous antibiotics at the time of their joint surgery however, this cannot possibly cover all types of infection which may be encountered. Infection in the postoperative period in most patients is treatable. It may require longer hospitalisation, treatment with antibiotics for a longer period than normal and washout of the joint.

In some cases, the implant will be removed to treat the infection before reimplanting a new joint. In rare cases when the infection cannot be treated successfully, a patient may need to have the artificial joint removed permanently. Infection is uncommon and we take precautions to avoid this problem.

Delayed infection has been reported years after joint replacement, and appears to be related to the ability of the implants, in general, to harbor bacteria transported by the blood stream from other sites of the body. Bladder or kidney infections can be a source but dental abscesses, infected ingrown toe nails, or skin infections may also be a significant danger to a joint implant.

Please call the office, or contact your family doctor if infection is suspected in any area. If dental surgery, bladder surgery, bowel surgery or rectal surgery is planned, the physician or dentist should be informed that you have had a joint replacement.

Blood Clots (The medical term for this is Deep Venous Thrombosis)

Another potential risk is the occurrence of blood clot or thrombosis after a joint replacement. Because our patients are mobilised very soon after surgery, this potential risk is small. In addition to early mobilisation patients are treated with calf compressors to prevent Thromboembolic disease (the development of clots in the lower extremities) during surgery. Post surgery TED stockings and low doses of aspirin or other anticoagulation (blood thinners) medications are prescribed depending on the patient’s medical history.

In patients without any history of thromboembolic problems we advise taking aspirin, 300 mg per day, for a period of six weeks.

These measures are in place to reduce the risk of forming a clot. In the event the patient is diagnosed with a blood clot intravenous or subcutaneous anticoagulation therapy may be required. However, some clots are small and of no clinical significance and so do not require any specific treatment other than the aspirin. This needs to be assessed on a case-by-case basis. If full anticoagulation is required however, this means a longer stay in hospital for the patient.

There is no perfect treatment and while trying to decrease the significant risk of deep vein thrombosis and the possibility of more serious complications such as pulmonary embolism (blood clots breaking off and traveling to the lungs), other potential side effects (such as bleeding) can occur with the drugs used to decrease this complication. These medications require extreme care in their use.

Nerve Damage

Nerve damage is another potential risk factor when considering joint replacement surgery. The nerves can be traumatised at the time of the operation through stretching and occasionally due to postoperative swelling. Precautions are in place to protect the nerves via superior surgical technique but the risk nevertheless, exists for these potential complications to occur. The risk factors are small and are dependant on the age and prior medical condition of the patient.

Diabetes, smoking and peripheral vascular disease are risk factors, as is the presence of previous back problems.

If nerve damage occurs rest and further examination of the nerve will be required and possible further surgery.

This is a rare complication of knee replacement surgery but can lead to weakness or altered feeling in the foot and ankle. It usually improves but can be permanent.

Ligament injuries

There are a number of ligaments surrounding the knee. These ligaments can be torn during surgery or break or stretch out any time afterwards. Although rare, surgery may be required to correct this problem.

Stiffness in the Knee

Ideally your knee should bend beyond 100 degrees but on occasion, the knee may not bend as well as expected. Sometimes manipulations are required. This could mean going to the operating room again where the knee is bent for you and under anesthetic.

Loosening of the Knee Replacement Implant

A small percentage of patients require revision surgery because of excessive wear or loosening of the prosthesis. This may cause pain and a limp, and the diagnosis can be confirmed with x-rays.
Excessive wear of the plastic liner is one of the most common reasons why revision knee surgery is performed.

Over 95% of patients who have a knee replacement have excellent relief of pain and improved mobility. Most patients never require a re-do of the knee replacement.


Dislocation is an extremely rare condition where the ends of the knee joint lose contact with each other or the plastic insert can lose contact with the tibia (shinbone) or the femur (thigh bone) which would cause acute pain and the inability to walk. It is more common in the first few weeks postoperatively and there are precautions that you can take to minimise this complication.

Leg Length Discrepancy

Every endeavor is made to maintain the legs at equal leg length, however, sometimes the leg can be slightly lengthened as a result of the knee replacement. This is also due to the fact that a corrected knee is more straight so sometimes unavoidable.

9Estimate of Fees

Generally our ‘Estimate of Fees’ is accurate however, on occasion unforeseen circumstances can arise during the operation which may require additional medical services or a different, more costly prosthetic device to be used. If this happens there may be additional costs to you that are not covered by the estimate.

This will be fully explained to you after the operation should it occur.

Estimate of Fees

        • Aftercare Consultation Fees

There will be 2 ‘no charge’ consultations after your Partial Knee Replacement procedure.

Follow-Up Appointments

Aftercare appointments with Professor Kohan following your procedure include:

        • 7 Days Post Surgery – This appointment is in order to check the skin cut & for Professor Kohan to asses your overall recovery.
        • 14 Days Post Surgery – At this appointment the skin clips will be removed. An ultrasound will also be done by our radiographer in the rooms in order for Professor Kohan to check for blood clots.
        • 6 Weeks Post Surgery – At this appointment Professor Kohan will asses the X-ray and monitor your overall recovery.

Any additional consultations after this time attract a fee which is reimbursed in part from Medicare.

      • Professor Kohan’s Surgical Fees

Medical Item No: 49517

      • Surgical Assistant Fees

The surgical assistant fees will either be billed to you directly or Professor Kohan will bill you on his behalf.

      • Anesthetic Fees

You will meet with Dr Kerr, the anaesthetist before your operation so that you can obtain an estimate of his fees. These will be billed to you directly.

      • Hospital Fees

These fees should be discussed with the hospital directly. Please be sure to check with your health fund regarding an gap or out of pocket expoenses.

      • Prosthetic Fees

If you are privately insured the prosthesis used in a Total Knee Replacement procedure is usually fully covered by your Health fund.

      • Ultrasound Fees

These fees are payable directly to the sonographer.