Unicompartmental Knee Replacement

What is a Unicompartmental Knee Replacement?

A unicompartmental (or partial) knee replacement resurfaces only the part of the knee affected by arthritis, leaving the healthy compartments and ligaments untouched. The knee has three compartments — the medial (inner), lateral (outer), and patellofemoral (between the kneecap and femur). Where arthritis is confined to just one of these, a partial replacement can address the damaged area without replacing the entire joint.

By preserving more of the natural knee — including healthy cartilage and the cruciate ligaments — a partial replacement aims to retain a more natural feel and movement than a total knee replacement, while relieving the pain of localised arthritis.

Who is Suitable?

Partial knee replacement is appropriate for carefully selected patients whose arthritis is limited to a single compartment. Suitability depends on factors such as:

• Arthritis confined to one compartment, confirmed on imaging
• Intact and functioning ligaments, particularly the cruciate ligaments
• Adequate range of motion and acceptable alignment
• The pattern and extent of disease in the rest of the knee

Not everyone with knee arthritis is a candidate. Where arthritis affects more than one compartment, a total knee replacement is generally more appropriate. Careful assessment determines the right option for each patient.

The Procedure

The damaged surfaces of the affected compartment are removed and resurfaced with metal components, with a plastic (polyethylene) spacer providing a smooth bearing surface. Because only part of the joint is addressed, the incision and the amount of bone removed are typically smaller than in a total knee replacement. Surgery is performed under spinal or general anaesthesia.

Benefits and Considerations

In suitable patients, partial knee replacement may offer:

• A faster recovery than total knee replacement
• Preservation of more of the natural knee and ligaments
• A more natural-feeling knee for some patients
• A smaller procedure with less bone removed

The main consideration is that arthritis can progress in the other compartments over time, which may eventually require conversion to a total knee replacement. Appropriate patient selection is key to good long-term outcomes.

Recovery

Recovery is often quicker than after a total knee replacement, with many patients mobilising soon after surgery. As with any joint replacement, a structured rehabilitation programme to restore strength, movement, and function is important, and your specific recovery plan will be tailored to your progress.

Risks and Complications

As with any major surgery, partial knee replacement carries risks, including:

• Infection
• Blood clots (deep vein thrombosis or pulmonary embolism)
• Bleeding
• Stiffness
• Ongoing pain
• Implant loosening or wear over time
• Progression of arthritis in the other compartments, potentially requiring further surgery

All relevant risks will be discussed in detail at your consultation.

Frequently Asked Questions

Am I a candidate for a partial knee replacement?

Suitability depends on arthritis being limited to one compartment, the condition of your ligaments, your alignment, and the rest of the knee. This is determined through clinical examination and imaging, and not everyone with knee arthritis is a candidate.

How is it different from a total knee replacement?

A partial replacement resurfaces only the affected compartment and preserves the rest of the knee, whereas a total knee replacement resurfaces the whole joint. A partial replacement is a smaller procedure that may allow a quicker recovery, but it is only suitable when arthritis is confined to one compartment.

Might I need a total knee replacement later?

It is possible. Arthritis can progress in the previously unaffected compartments over time, and if it does, a partial replacement can be converted to a total knee replacement. Careful patient selection helps reduce this likelihood.

Medical Disclaimer
The information on this page is intended as general patient education and does not constitute medical advice. Every patient is different, and treatment decisions should always be made in consultation with a qualified medical professional based on your individual circumstances, health history, and imaging. Outcomes from surgery vary between patients and cannot be guaranteed. If you have concerns about your knee health or are considering surgery, please contact Dr Slattery’s rooms to arrange a consultation.