Partial Knee Replacement

What are the risks of having knee replacement surgery? +

General complications of knee replacement surgery can include:

Infection

The risk is less than 1 in 400 of developing an infection. This can occur despite using a sterile surgical technique and giving pre-operative intravenous antibiotics.

If the infection involves only the wound (superficial), it may just need treatment with a course of antibiotics.

If a deep knee joint infection occurs, it may require more surgery to wash out the knee as well as intravenous antibiotics. During the final washout, the plastic liner within the knee may be removed and replaced with a new sterile liner in order to decrease the bacterial load.

If this fails to control the deep infection, the knee replacement may require removal, and an antibiotic impregnated cement spacer may be inserted. After an appropriate period of intravenous antibiotics, if the deep infection is cured, the cement spacer may be removed and a new knee replacement reimplanted.

Bleeding

Bleeding can occur around the incision or into the knee joint itself. This is usually self-limiting, but on rare occasions will require re-operation to wash out the accumulated blood.

Deep vein thrombosis

Clots can occur in the deep veins of the leg that may dislodge and occlude the arteries in the lungs. DVT presents as leg pain and swelling after your operation. The diagnosis is confirmed with an ultrasound scan and, depending on the type of DVT, may require treatment with blood thinners.

**Specific complications of knee replacement surgery can include: **

Ongoing pain

Despite the knee replacement being performed well, 1 in 10 people are dissatisfied with the end result. This is in the absence of any problem in the knee such as infection, loosening, or incorrect alignment of the knee replacement.

Stiffness

The knee can become stiff after surgery due to the formation of scar tissue. This stiffness usually resolves with physiotherapy but can sometimes persist. If the knee is not bending or straightening adequately 6-8 weeks post-operatively, a manipulation procedure may be required. This involves putting the patient to sleep and pushing on the knee to break the scar tissue.

Instability

Whilst performing a knee replacement, attention is given to making sure the fit is tight enough to give the knee stability. but loose enough to allow motion. It’s rare, but sometimes damage to the surrounding ligaments or incorrect sizing or placement of the prosthetic components can result in the knee feeling unstable. If this occurs, it may require a revision procedure to address the instability.

Intraoperative fracture

This is an uncommon risk and usually occurs in patients with osteoporosis during preparation of the bone surfaces for prosthetic implantation. Significant fractures require surgical fixation with metal screws and potentially a metal plate. A stem may need to be added to the prosthesis in order to bypass the load through the fracture site.

Loosening

Loose microscopic particles from the plastic liner of the knee replacement can induce a bodily response that causes the loss of bone around the prosthesis (osteolysis). With time, this can cause the prosthesis to loosen and cause knee pain with activity. Although the components are designed to survive 20 years or more in most cases, loosening can sometimes occur early. Symptomatic loosening necessitates a revision procedure.

Need for a revision procedure

If the plastic implant becomes worn over time, the components loosen, or there are issues with stability or positioning of the prosthesis, it may require a revision procedure.

Disease progression

This situation applies to partial knee replacements where only one of the three components of the knee is replaced. Sometimes with time, the arthritis progresses to involve the other two components the knee and leads to patient symptoms. If this is the case, there is an option to revise the partial knee replacement to a total knee replacement.

Am I a suitable candidate for a partial knee replacement? +

40% of patients with knee osteoarthritis are suitable candidates for a partial knee replacement. If arthritis affects only one knee compartment, and you don’t have a significant deformity or stiffness in your knee, this procedure may suit you.

In general, people with rheumatoid arthritis or other types of inflammatory arthritis are not suitable for this procedure because the arthritic change may affect all parts of the knee and cause failure.

Mr Pai will obtain a focused series of knee X-rays and may organise for a special alignment X-ray from your hip to your ankle. These are called long-limb alignment views. These X-rays allow him to determine which compartments are affected by arthritis and the overall alignment at your knee. If there is any doubt whether the arthritic process affects other compartments, he will obtain an MRI of your knee.

Is performing a partial knee replacement easier?

Performing a succesful partial knee replacement is more challenging than a total knee replacement. Experience in performing partial knee replacement is essential to obtain a good outcome.

The Australian Joint Registry shows that the revision rate of unicompartmental knee replacements is between 10-15% percent at 10 years. Although this is comparably higher than a total knee replacement, this can be explained simply. The Joint Registry is the average result of all orthopaedic surgeons in Australia. It has been shown that surgeons who perform unicompartmental knee replacements on a regular basis have a much lower revision rate than those that don’t. Studies have shown that at least 20% of the knee replacements that a surgeon performs should be a unicompartmental knee replacement, to optimise the postoperative outcome.

During his time in the United Kingdom, Mr Pai was trained to perform conventional unicompartmental knee replacements using the uncemented Oxford prosthesis. Worldwide, this is one of the most commonly used prostheses for a partial knee replacement.  Subsequently, Mr Pai was trained to use robotic assistance to perform this operation.

What are the advantages of a partial knee replacement? +

The rate of patient dissatisfaction following a total knee replacement can be high. Some studies quote 15-20%. The rate of dissatisfaction following a well-performed unicompartmental knee replacement is lower. This is because the knee is able to function more like a normal knee does. A unicompartmental knee replacement preserves the ligaments inside your knee. The other compartments that are not affected by arthritis are left alone. The operation is smaller than a total knee replacement and has less blood loss.

What are the disadvantages of a partial knee replacement? +

Sometimes, arthritis will progress to involve other compartments in the knee, and patients may develop pain from arthritis in a different location. This will require a revision to a total knee replacement. This revision is technically straightforward, and it has a high success rate.

When compared to a total knee replacement, a unicompartmental knee replacement has a higher rate of revision surgery. The revision rate is significantly reduced when a surgeon regularly performs partial knee replacement surgery, uses robotic assistance and selects appropriate patients for this procedure.

What is the role of robotic knee surgery? +

Robotic surgery is a useful adjunct when knee replacement surgery. It can improve the alignment of the knee components compared to performing the operation using conventional methods. Early results suggest that robotically assisted partial knee replacements have a lower revision rate. These findings are reflected in the data collected on the Australian Joint Registry. Click here to read more about robotic knee surgery.

Do I need a knee replacement? +

A knee replacement is performed to relieve pain from arthritis & improve the quality of your life. Healthy cartilage within the joint allows the joint to move smoothly and without pain. With arthritis, the cartilage inside the joint wears out and causes pain.

With early arthritis strengthening the thigh muscles and encouraging movement in the knee with a physiotherapist can help improve the pain. Painkillers can also be helpful in decreasing the amount of pain.

As the arthritis progresses and the pain gets worse it may decrease your ability to walk and perform activities you enjoy. Occasionally, patients may complain of knee pain that wakes them up at night.

Once the pain is no longer adequately controlled with non-operative measures you should seek a specialist opinion from an orthopaedic knee surgeon to talk about the option of having a knee replacement.

Does a knee replacement feel like a normal knee? +

Although the knee will feel more natural by one year after the operation for some patients it may not feel normal. Even so, most patients are extremely happy with their outcome as their pain from arthritis has been alleviated.

How long do knee replacements last? +

The results from our national joint registry shows that the average medial unicompartmental knee replacement performed for osteoarthritis will have an 80% chance of working well at 15 years. The revision rate is slightly higher if you under the age of 65. Robotics has been shown to improve the revision rate of a partial knee replacement.

What are knee replacements made from? +

The components that are attached the femur and tibia are made from colbalt-chromium and titanium, respectively. There is a medical grade plastic insert inserted between the femoral and tibial components which is made from polyethylene.

Will I have a numb patch around my scar? +

The incision needed to perform a knee replacement sacrifices some of the smaller nerve branches that supply the skin around the knee. As a result, patients will have a small area of permanent numbness on the outside of their knee replacement scar. This is expected and will not affect the way the knee replacement works.

Will I be able to kneel? +

Kneeling will not damage the knee replacement. However, many patients find it difficult to kneel for several months after the operation as the surgical scar can be sensitive. Kneeling usually becomes easier as time passes by. Using of a foam knee pad while kneeling is recommended.

How long does swelling after a knee replacement last for? +

The swelling in the knee and the surrounding soft tissues can last for 4-6 months after your surgery.

Will I need hospital based rehabilitation? +

It is ideal to be discharged back to your own house to continue your rehabilitation. However, our hospital based physiotherapists will assess your safety when mobilising after the operation. If you need some more help in the early stages of your recovery, a period of inpatient rehabilitation may be beneficial.

Will my knee replacement set off a metal detector at an airport? +

Yes, a knee replacement will trigger the metal detectors at an airport. Be proactive and advise the security guards that you have had a knee replacement. Wear clothing where the knee incision can easily be shown to the security staff. Having a letter or medical certificate will not prevent these security measures.

Will my knee look different after a knee replacement? +

With severe arthritis the knee can look bowed prior to your knee replacement. During the knee replacement the aim is to correct your alignment to what is was prior to the onset of arthritis. Your knee will look straighter than it was in this situation.

Will my leg be longer? +

If you have severe arthritis with bowing of the leg, the knee replacement surgery will correct your alignment to make your knee straighter. In the process, the length of your limb may be increased on the operated side by a small amount. On average, there is an increase in length by 3-4 millimetres. With time, the majority of patients get accustomed to this difference.

Why does my knee replacement makes a clicking noise? +

This is usually normal and related to the sound of the plastic insert hitting the metal component of the knee replacement when you walk. Most patients experience this and it is not a harmful situation.

When can I drive after a knee replacement? +

You will not be able to drive for 6 weeks following a knee replacement. You must be off strong painkillers, be walking without crutches and have a relatively painfree range of motion in the affected knee before you commence driving.

When can I swim? +

The wound should be kept dry for two weeks following the operation. Once the wound healing is reviewed at your 2-week post-operative consultation you will be able to shower with no wound dressings on. Participating in pool based rehabilitation or swimming is not recommended for 4 weeks after your operation as it may increase the risk of infection.

Do I need antibiotics after a knee replacement for dental work? +

Avoid non-urgent dental procedures and dental cleaning for 3 months following a knee replacement. If you require urgent dental work within this timeframe then antibiotics should be given by your dentist to prevent bacteria from getting into the bloodstream and travelling to the knee joint.

If you require dental work more than 3 months after your knee replacement then routine antibiotics do not need to be given with dental work unless you are in a situation where your immune system doesn’t function as well. This situation includes patients with diabetes, those on oral steroids or immune suppressing drugs. If you are in doubt, please get your dentist to contact us prior to your dental procedure.