Partial Knee Replacement

What is a Partial Knee Replacement?

UKR replaces only the arthritic part of the knee while preserving healthy joint structures.

A partial knee replacement, also called a unicompartmental knee replacement (UKR or UKA), replaces only the part of the knee affected by arthritis rather than replacing the entire joint.

The knee can be divided into three main compartments:

• the medial compartment on the inside of the knee
• the lateral compartment on the outside
• the patellofemoral compartment between the kneecap and thigh bone

Most partial knee replacements are performed for arthritis affecting only the medial compartment.

Unlike a total knee replacement, the healthy parts of the knee are preserved. The aim is to reduce pain while retaining as much of the patient's natural knee anatomy, ligaments and movement as possible.

Why is Partial Knee Replacement Surgery Done?

UKR may suit arthritis confined to one part of the knee with suitable ligaments and alignment.

A partial knee replacement can be considered when advanced arthritis is limited predominantly to one part of the knee and the remaining compartments are sufficiently healthy.

It may be appropriate when:

• pain comes predominantly from one side of the knee
• X-rays show advanced arthritis isolated to one compartment
• the other parts of the knee remain reasonably well preserved
• the knee has suitable ligament stability
• deformity and stiffness remain within a range that can be corrected

A partial knee replacement is not suitable for every patient with knee arthritis.

If arthritis is widespread throughout the knee, there is major deformity or instability, or other parts of the knee are significantly damaged, a total knee replacement may be more appropriate.

Choosing between partial and total knee replacement therefore requires careful assessment of your symptoms, examination and imaging.

How is Partial Knee Replacement Surgery Performed?

Only the damaged compartment is resurfaced while healthy parts of the knee are preserved.

The operation has similarities to a total knee replacement, but considerably less of the knee is replaced.

1. Anaesthetic

A spinal or general anaesthetic may be used, together with additional pain relief around the knee.

2. Accessing the knee

An incision is made at the front of the knee. Because only one compartment is being replaced, the operation can generally be performed through a smaller surgical exposure than a total knee replacement.

3. Checking the knee

The affected compartment and the remainder of the knee are carefully assessed.

Occasionally, surgery may need to be changed to a total knee replacement if the arthritis is found to be more extensive than expected.

4. Preparing the damaged compartment

A small amount of damaged bone and cartilage is removed from the affected side of the femur and tibia.

The healthy cartilage, bone and important ligaments in the remainder of the knee are preserved.

5. Placing the partial knee replacement

Small metal components cover the worn surfaces of the femur and tibia.

A strong plastic bearing sits between these components, creating a new smooth surface for that part of the knee.

The implants may be fixed using bone cement or a cementless technique depending on the implant and individual circumstances.

6. Closing the knee

The deeper tissues are repaired using strong sutures and the incision is closed in several layers with absorbable sutures.

I generally close the skin with a fine absorbable suture underneath the skin and use a glued mesh over the incision. This provides additional support while the skin heals.

Preparing for Partial Knee Replacement Surgery in Brisbane

Preparation focuses on health, strength, medications and planning for recovery.

Although partial knee replacement is generally a smaller operation than total knee replacement, preparation remains important.

Health optimisation

Before surgery:

• stop smoking or vaping if possible
• optimise diabetes and other medical conditions
• maintain good nutrition
• improve general fitness where possible
• tell the team about previous blood clots, heart or lung problems and sleep apnoea
• provide a complete medication and supplement list

Pre-operative exercise

Maintaining knee movement and muscle strength can assist early recovery.

Exercises commonly focus on the quadriceps, hamstrings, hip muscles and knee range of movement.

Preparing your home

Arrange help with transport, shopping and other activities during early recovery. Remove trip hazards and prepare somewhere comfortable to rest, elevate the leg and perform exercises.

Your treating team will advise which medications should be continued or stopped before surgery.

As Brisbane has a warm and humid climate, particularly during the summer months, consider making sure you have access to a cool, comfortable and preferably air-conditioned environment during your early recovery. Apart from making recovery more comfortable, published research has found an association between warmer weather and higher rates of surgical-site infection, including research specifically examining infection following knee and hip replacement surgery. Keeping yourself comfortable and your surgical dressing clean and dry is therefore particularly important during Brisbane's warmer months.

What to Expect After Partial Knee Replacement

Recovery involves early walking followed by progressive rehabilitation and strengthening.

In hospital

Partial knee replacement can often have a faster early recovery than total knee replacement.

Patients generally begin walking soon after surgery with assistance from a physiotherapist. Hospital stay varies and some suitable patients may be able to leave hospital the following day.

First 2–6 weeks

Walking commonly progresses from crutches or a frame to a stick and then independent walking.

Swelling and bruising are normal but may settle more quickly than after a total knee replacement.

Physiotherapy focuses on:

• restoring knee movement
• improving quadriceps strength
• normalising walking
• gradually returning to everyday activities

Driving should only resume when you can safely and confidently control the vehicle and are no longer affected by medications that impair driving.

6 weeks to 3 months

Most patients have made substantial progress with walking and everyday activities.

Strength and endurance continue to improve and exercise can gradually become more demanding.

3 to 12 months

Further improvement in strength, confidence and knee function can continue for many months.

Some patients report that a partial knee replacement feels more like their natural knee than a total knee replacement. A 2025 systematic review and meta-analysis comparing joint awareness after partial and total knee replacement found lower joint awareness after partial knee replacement, although there was considerable variation between the studies and this outcome cannot be guaranteed for an individual patient.

Long-Term Outcomes After Partial Knee Replacement Surgery

Partial knee replacement can improve pain and function, but revision risk is higher.

Pain relief and function

For appropriately selected patients, both partial andtotal knee replacement can provide substantial improvement in pain and function.

The TOPKAT randomised controlled trial comparing partial and total knee replacement found that both procedures produced good clinical outcomes at five years for patients with isolated medial compartment osteoarthritis.

More recently, 10-year follow-up of the TOPKAT trial has provided further long-term evidence comparing these two approaches.

Partial versus total knee replacement

There are advantages and disadvantages to each procedure.

A large systematic review and meta-analysis published in theBMJ found that partial knee replacement was associated with shorter hospital stays and favourable results in several patient-relevant outcomes. However, revision surgerywas more common after partial knee replacement than after total knee replacement.

This trade-off is important when deciding which operation is appropriate.

How long does a partial knee replacement last?

Partial knee replacements can function well for many years, but their revision rate is generally higher than that of total knee replacement.

A major systematic review of long-term knee replacement survival found that national registry data suggested approximately 70% of unicompartmental knee replacements remained unrevised at 25 years, compared with approximately 82% of total knee replacements.

These are population-level estimates and cannot predict how long an individual knee replacement will last.

What happens if arthritis progresses?

Because a partial knee replacement leaves the other compartments intact, arthritis can sometimes progress elsewhere in the knee over time.

If the implant fails or arthritis progresses significantly, the partial knee replacement can often be revised to a total knee replacement. Revision surgery, however, can be more complex than a first-time knee replacement.

Things to Look Out for After Partial Knee Replacement

Increasing pain, wound problems, swelling or breathing symptoms need medical review.

Contact our office, your GP, or seek urgent medical attention if you notice:

Possible infection

• increasing redness, warmth or swelling
• increasing pain after initial improvement
• wound leakage or pus
• fever or feeling significantly unwell

Infection is uncommon but potentially serious after any joint replacement.

Possible blood clot

Seek assessment for:

• new calf pain or tenderness
• significant one-sided leg swelling
• sudden shortness of breath or chest pain

Sudden breathing symptoms require emergency assessment.

Wound problems

Persistent leakage, opening of the incision or rapidly increasing swelling should be reviewed.

Knee stiffness

Difficulty regaining movement despite exercises and physiotherapy should be discussed with your treating team.

Persistent or new knee pain

Ongoing pain does not necessarily mean that the implant has failed. However, new pain after initially doing well, increasing swelling, or pain developing in another part of the knee should be assessed.

Partial Knee Replacement Brisbane

Dr Alexey Borshch is a specialist orthopaedic surgeon in Brisbane with a particular clinical focus on surgery of the hip, knee and lower limb.

His practice as a Brisbane Orthopaedic Surgeon focuses on the assessment and treatment of knee arthritis, as well as performing knee replacement surgery, which includes both total knee arthroplasty and partial knee replacement.

Dr. Borshch completed his medical degree at the University of Queensland before undertaking specialist orthopaedic training in Queensland. He completed the Australian Orthopaedic Association training program and the Royal Australasian College of Surgeons Fellowship Examination in Orthopaedic Surgery. He obtained specialist registration in Orthopaedic Surgery in 2022 and is a Fellow of the Australian Orthopaedic Association.

He offers consultations in Hamilton, Brisbane, and conducts private orthopaedic surgery at Brisbane Private Hospital.