Partial knee replacement, also called unicompartmental knee replacement (UKA), is a type of knee replacement in which only the damaged part of the knee is replaced.

Unlike total knee replacement, which replaces the damaged surfaces throughout the knee, partial knee replacement preserves the healthy parts of the joint.

It can be an excellent treatment for selected patients whose arthritis is mainly limited to one part of the knee.

What is a partial knee replacement?

The knee has three main compartments:

• The inner compartment

• The outer compartment

• The kneecap compartment

In some people, arthritis mainly affects one of these compartments while the remaining parts of the knee are relatively healthy.

In a partial knee replacement, only the damaged compartment is replaced with artificial components. The healthy parts of the knee are preserved.

The most commonly performed partial knee replacement is for arthritis affecting the inner (medial) compartment of the knee.

Why might I need a partial knee replacement?

Partial knee replacement may be considered when arthritis is causing:

• Persistent knee pain

• Difficulty walking

• Pain while climbing stairs

• Difficulty with everyday activities

• Pain during activities that you enjoy

• Stiffness or reduced function

It is particularly useful when the arthritis is mainly limited to one compartment of the knee and the rest of the knee is in good condition.

Do I need a partial knee replacement if I have arthritis?

Not necessarily.

Having arthritis does not automatically mean that you need a knee replacement.

Treatment depends on the severity of your symptoms, the condition of your knee and how much arthritis is affecting your daily life.

When symptoms are manageable, treatment may include exercise, physiotherapy, activity modification, medicines when appropriate and other non-surgical treatments.

A partial knee replacement is considered when the arthritis is causing significant symptoms and the affected part of the knee is suitable for replacement.

Who is suitable for a partial knee replacement?

Partial knee replacement is most suitable when:

• Arthritis is mainly limited to one compartment

• The remaining parts of the knee are relatively healthy

• The major supporting ligaments of the knee are functioning well

• The knee has a suitable pattern of deformity and movement

• Pain is mainly coming from the damaged compartment

• Non-surgical treatment is no longer providing enough relief

Your symptoms, examination and X-rays are all important when deciding whether partial knee replacement is appropriate.

How is partial knee replacement different from total knee replacement?

The main difference is how much of the knee is replaced.

Partial knee replacement: Only the damaged compartment is replaced, while the healthy parts of the knee are preserved.

Total knee replacement: The damaged surfaces throughout the knee are replaced.

For a patient who is suitable for both procedures, partial knee replacement may offer advantages such as preserving more of the natural knee and allowing a more natural-feeling movement.

However, partial knee replacement is only suitable when the disease is appropriately limited.

What happens during partial knee replacement?

During the operation, the damaged surfaces of the affected part of the knee are carefully removed.

They are then replaced with artificial components that recreate the joint surface.

The healthy parts of the knee are preserved.

The aim is to relieve pain while maintaining as much of the patient's natural knee as possible.

What are the advantages of partial knee replacement?

For appropriately selected patients, partial knee replacement can offer several advantages:

• More of the natural knee is preserved

• Less bone is removed

• The knee may feel more natural after recovery

• Recovery can be quicker than after total knee replacement

• Less disruption to the surrounding tissues

• Many patients can return to normal daily activities relatively quickly

Because the healthy parts of the knee and much of the natural knee structure are preserved, many patients describe the knee as feeling more like their own knee after recovery.

Is partial knee replacement better than total knee replacement?

Neither operation is better for every patient.

The right operation depends on the pattern of arthritis and the condition of the rest of the knee.

If arthritis is limited mainly to one compartment and the rest of the knee is healthy, partial knee replacement can provide excellent results.

If arthritis affects several parts of the knee, total knee replacement is usually more appropriate.

The aim is to choose the operation that best matches the condition of your knee.

How long does a partial knee replacement last?

Modern partial knee replacements can provide long-lasting pain relief and good function.

Many patients continue to have a well-functioning partial knee replacement for many years.

The longevity of the implant depends on several factors, including the condition of the knee, activity level, body weight, implant design and surgical technique.

A partial knee replacement can also be converted to a total knee replacement in the future if arthritis develops in other parts of the knee or the implant develops a problem.

What should I expect after partial knee replacement?

Recovery is usually gradual, but many patients can begin walking soon after surgery.

The early focus is on:

• Controlling pain and swelling

• Regaining knee movement

• Walking comfortably

• Improving muscle strength

• Returning gradually to normal activities

Because less of the knee is replaced and more of the natural knee is preserved, recovery can be faster for many patientscompared with total knee replacement.

The exact recovery time varies from person to person.

When can I walk after partial knee replacement?

Most patients are encouraged to stand and walk soon after surgery, depending on their individual condition and the surgeon's advice.

You may initially use a walker or another form of support.

As your strength and confidence improve, you can gradually return to walking without support.

Can I exercise after partial knee replacement?

Yes.

Regular physical activity is an important part of maintaining a healthy knee and overall health after recovery.

Activities such as:

• Walking

• Cycling

• Swimming

• Golf

• Gym-based strengthening

• Other low-impact activities

can generally be continued.

Your surgeon can guide you regarding activities that are appropriate for your knee and level of recovery.

Will a partial knee replacement feel like a normal knee?

One of the potential advantages of partial knee replacement is that more of your natural knee is preserved.

Many appropriately selected patients report that the knee feels natural after recovery, and some are able to forget that they have a knee replacement during everyday activities.

However, the experience varies between individuals.

The final result depends on the condition of the knee, the surgery, rehabilitation and individual factors.

What are the risks of partial knee replacement?

Partial knee replacement is a well-established procedure with good outcomes in appropriately selected patients.

As with any surgery, complications can occur. These may include:

• Infection

• Blood clots

• Stiffness

• Persistent pain

• Implant wear or loosening

• Progression of arthritis in another part of the knee

• Need for further surgery

Your surgeon will discuss the risks relevant to your individual circumstances before surgery.

Can a partial knee replacement become a total knee replacement?

Yes.

If arthritis develops in another part of the knee or the partial knee replacement develops a problem over time, it may be necessary to convert the partial knee replacement to a total knee replacement.

This is one reason why careful patient selection is important before partial knee replacement.

However, the possibility of needing further surgery in the future should not by itself discourage a suitable patient from considering partial knee replacement.

When should I consider partial knee replacement?

You may be a candidate for partial knee replacement when:

• Your knee pain is affecting your everyday life

• Arthritis is mainly limited to one compartment

• The rest of your knee is in good condition

• Appropriate non-surgical treatment is no longer providing enough relief

• Your examination and X-rays suggest that partial knee replacement is suitable

The decision should be based on a detailed assessment of your knee rather than on the X-ray alone.

Frequently asked questions

Can I have a partial knee replacement if I have arthritis in both knees?

Yes.

Having arthritis in both knees does not automatically rule out partial knee replacement.

Each knee is assessed separately. If arthritis in a particular knee is mainly limited to one compartment and the rest of the knee is suitable, partial knee replacement may be an option.

Is partial knee replacement a smaller operation?

Partial knee replacement generally involves replacing less of the knee and preserving more of the natural joint.

This can contribute to less tissue disruption and a faster recovery in appropriately selected patients.

However, it is still a major surgical procedure and requires proper rehabilitation.

Will I be able to bend my knee after partial knee replacement?

Yes.

Good knee movement is one of the important goals of the operation.

Most patients can achieve useful knee movement for walking, climbing stairs and everyday activities, although the final range varies between individuals.

Can I return to sports after partial knee replacement?

Many patients can return to recreational activities after recovery.

Low-impact activities are generally encouraged. More demanding activities should be discussed with your surgeon and resumed gradually.

What if I am not suitable for partial knee replacement?

If arthritis affects several parts of the knee, or if the knee has other problems that make partial replacement unsuitable, total knee replacement may be a better option.

The goal is not to perform a partial replacement whenever possible, but to choose the operation that gives the patient the best long-term result.