Partial Knee Replacement (Unicompartmental Knee Replacement) in Bristol

Not all knee arthritis needs a total knee replacement. When the wear is mainly in one compartment – and the rest of the knee is healthy – a partial knee replacement (also called a unicompartmental knee replacement or UKR) can be a better option: a smaller operation, faster recovery, and a knee that typically feels more natural afterwards. The catch is that it has to be the right knee for the procedure. Getting that decision right is the most important part.

What is a partial knee replacement?

The knee has three compartments: the medial (inner side), the lateral (outer side) and the patellofemoral (behind the kneecap). In a partial replacement, I resurface only the worn compartment with metal and plastic components. The healthy cartilage, the cruciate ligaments and the undamaged parts of the joint are all left intact.

The most common type is a medial UKR – resurfacing the inner compartment – because that is where arthritis most frequently develops. But I also perform lateral and patellofemoral replacements when the pattern fits.

Why patients consider this operation

By the time someone is sitting in front of me discussing a partial knee replacement, the story is usually similar: knee pain that has been gradually worsening, limiting walking distance, making stairs difficult, and eating into activities they enjoy – cycling, hiking, the gym, golf. They have tried physio, possibly had injections, and the pain is still there. Their goals are typically:

Getting rid of the arthritis pain
Walking further and more confidently
Getting back to exercise and the activities they have been missing
Reducing reliance on painkillers

Assessment

The decision about whether a partial replacement is right for you starts with working out exactly what is going on in your knee. I need to know which compartment is causing the pain, what the other compartments look like, and how the knee behaves mechanically.

In practice, this means a detailed history and examination – alignment, stability, range of motion, where the tenderness is, how the kneecap tracks. I will get weight-bearing x-rays to see the arthritis pattern under load (a non-weight-bearing x-ray can make things look better than they are). If there is any uncertainty about the pattern, or I need more information on the cartilage, meniscus or ligaments, I will arrange an MRI.

The goal is to be confident that your arthritis is predominantly in one compartment and that a partial replacement is the best option – not just an option.

Who is suitable?

A partial knee replacement works best when arthritis is mainly confined to one compartment and the rest of the knee is in good condition.

Good candidates typically have:

Pain localised to one side of the knee (usually the inner side)
Imaging showing arthritis predominantly in one compartment, with reasonable cartilage elsewhere
A stable knee with correctable deformity – meaning the leg straightens out when I stress it
A functional range of movement
An intact and functioning ACL

A total replacement is more appropriate when:

Arthritis is significant in more than one compartment
There is marked stiffness, fixed deformity or significant instability
There is widespread inflammatory arthritis

Age alone does not determine suitability – the arthritis pattern and the condition of the whole knee do.

Non-surgical options

I always want to know that a patient has had a proper trial of non-surgical treatment before we discuss surgery. Depending on the situation, this might include:

Targeted physiotherapy – building quad and hip strength, improving movement control
Weight management and activity modification
Pain relief and anti-inflammatory medication where appropriate
Injections – typically corticosteroid to settle a flare, though other options exist
An offloading brace to shift load away from the affected compartment

If symptoms remain genuinely limiting despite this, surgery becomes a reasonable conversation.

Partial vs total knee replacement

Advantages of a partial replacement

Smaller incision and less dissection – the knee is not fully opened up
Typically faster recovery and earlier return to function
Many patients describe a more natural-feeling knee, because the cruciate ligaments and healthy compartments are preserved
Preserves bone stock, which makes any future revision surgery more straightforward

Limitations

It is only suitable for specific arthritis patterns – it will not work well if arthritis is more widespread than expected
Arthritis can progress in the other compartments over time
Some patients will eventually need revision to a total replacement – though for many, this is years or decades later

I tell patients that the question is not "which operation is better?" – it is "which operation is right for your knee?"

The operation

Through a relatively small incision, I remove the worn cartilage and a thin layer of underlying bone from the affected compartment. A metal component is placed on the femur and tibia, with a plastic bearing between them to create a smooth, low-friction surface. The rest of the knee is left alone.

For some patients, I use robotic assistance to refine implant positioning and soft-tissue balance. I will discuss whether this adds value in your specific case.

Anaesthetic and hospital stay

I usually perform partial replacements under a spinal anaesthetic with sedation, often combined with a local anaesthetic nerve block for post-operative pain control. Many patients go home the same day; others stay one night depending on comfort, mobility and what support they have at home.

Recovery and rehabilitation

One of the genuine advantages of a partial replacement is that the recovery tends to be quicker and less punishing than after a total. Most people follow a staged rehabilitation plan:

Typical milestones

First 1–2 weeks: walking little and often with crutches, swelling management, gentle range-of-motion exercises, short outdoor walks
Weeks 2–6: improving walking distance, building stair confidence, progressive strengthening, restoring a normal walking pattern
Weeks 6–12: increasing endurance and returning to most day-to-day activities comfortably
3–6 months: continued strength gains and return to higher-level activities – cycling, gym, hiking – with ongoing rehabilitation as needed

Driving and work

Driving: depends on which leg was operated on, your reaction times and control, and your insurer's requirements
Work: desk-based roles can often return within a few weeks; physically demanding jobs typically need longer

Risks and complications

I discuss the specific risks with every patient before surgery. For a partial knee replacement, these include:

Infection
Blood clots (DVT / pulmonary embolus)
Stiffness or prolonged swelling
Persistent pain – uncommon, but some patients do not get the expected improvement
Progression of arthritis in the other compartments
Loosening, bearing wear, or need for further surgery over time

When to seek urgent advice after surgery

Increasing redness, heat, wound leakage, fever or feeling unwell
New calf pain or swelling, chest pain or shortness of breath
Sudden inability to weight-bear or a significant change in knee function

How long does a partial knee replacement last?

There is no single answer – it depends on activity level, body weight, bone quality, alignment and surgical technique. Many patients do very well for 15–20 years or more. When a partial replacement does eventually need revising, the most common reason is progression of arthritis in the remaining compartments or gradual bearing wear. Conversion to a total replacement is usually straightforward because healthy bone has been preserved.

Frequently asked questions

Is recovery easier than after a total replacement?

In most cases, yes. The operation is less invasive, the knee swells less, and people tend to regain movement and confidence more quickly. That said, you still need to take rehabilitation seriously – the result depends on what you put in.

Will it feel more natural than a total replacement?

Most patients who have had a well-indicated partial replacement describe the knee as feeling more like their own. The cruciate ligaments are still there, and the normal mechanics of the surviving compartments are preserved. The best predictor of that "natural" feeling is whether the operation was the right match for the arthritis pattern in the first place.

Can I kneel afterwards?

Some people manage to kneel comfortably; others find it remains a bit tender over the front of the knee. It tends to improve with time and practice. Your physiotherapist can help you build the confidence to do it safely.

Can I return to sport?

Most of my partial replacement patients get back to low-impact activities – cycling, swimming, hiking, gym work, golf. Higher-impact or pivoting sports are possible for some people, but I discuss this individually based on your knee, your fitness and the demands of the activity.

What if I have inner-side arthritis but also some kneecap pain?

This comes up a lot. The key question is whether the kneecap joint has genuine arthritis – cartilage loss visible on imaging – or whether the anterior pain is referred from the medial compartment. In many cases, the kneecap pain resolves once the worn compartment is dealt with. Careful assessment and imaging before surgery help distinguish the two.

Can I be assessed for a partial knee replacement in Bristol?

Yes. I see patients for partial knee replacement assessment at my clinics in Bristol. That includes working out whether a partial is the right option, discussing alternatives, and planning the surgery if we decide to go ahead.