Partial vs Total Knee Replacement: Key Differences

Partial and total knee replacement are surgical options used to treat knee joint damage, commonly from osteoarthritis. Both procedures involve replacing damaged bone and cartilage with artificial components, but they differ in how much of the knee is replaced.

The suitable option depends on the location and severity of knee damage, symptoms, knee stability, age, activity level, medical history, and the orthopaedic surgeon’s assessment.

What Is Knee Replacement Surgery?

Knee replacement, also called knee arthroplasty, involves removing damaged bone and cartilage from the knee and replacing them with metal and plastic components. It may be considered when knee pain, stiffness, and reduced function continue despite non-surgical treatment.

Before recommending surgery, an orthopaedic surgeon usually assesses knee movement, stability, strength, and imaging findings such as X-rays. X-rays can help show the extent of knee damage before deciding whether knee replacement is appropriate.

What Is Partial Knee Replacement?

Partial knee replacement, also known as unicompartmental knee replacement, replaces only the damaged compartment of the knee. The knee has three main compartments:

• Medial compartment: inner side of the knee
• Lateral compartment: outer side of the knee
• Patellofemoral compartment: front of the knee, between the kneecap and thighbone

Partial knee replacement may be considered when arthritis or damage is limited to one compartment of the knee.

What Is Total Knee Replacement?

Total knee replacement involves replacing the damaged surfaces across the knee joint. It is usually considered when arthritis or joint damage affects multiple compartments of the knee.

This may be more suitable for patients with widespread cartilage loss, deformity, reduced joint stability, or symptoms affecting several areas of the knee.

Key Differences Between Partial and Total Knee Replacement

Suitability: Who May Be Considered?

Partial Knee Replacement May Be Considered If:

• Knee damage is limited to one compartment
• Knee ligaments are functioning adequately
• Knee alignment is suitable
• Symptoms match the affected compartment
• There is no widespread inflammatory arthritis
• The patient meets clinical and imaging criteria

Partial knee replacement is not suitable for everyone. Only about 10% to 15% of patients assessed for possible knee replacement are candidates for partial knee replacement.

Total Knee Replacement May Be Considered If:

• Arthritis affects multiple knee compartments
• Pain is widespread across the knee
• There is notable stiffness or deformity
• Knee function is reduced despite non-surgical care
• Imaging shows broader joint damage
• The knee has instability or alignment concerns

Many patients have damage in two or more areas, making total knee replacement the more appropriate option for those cases.

Recovery Differences

Recovery varies from patient to patient. Factors such as age, general health, muscle strength, pain level, and rehabilitation participation can affect progress.

Partial knee replacement may allow a shorter hospital stay and early recovery for suitable patients. Partial knee replacement may involve less time in hospital compared with total knee replacement.

Total knee replacement may involve a longer rehabilitation period because more of the knee joint is replaced. However, both procedures usually require physiotherapy, walking practice, wound care, swelling control, and follow-up appointments.

Benefits and Limitations

Partial Knee Replacement

Possible considerations include:

• Treats only the damaged compartment
• May preserve more natural knee structures
• May involve a shorter early recovery in suitable patients
• May not be suitable if arthritis affects more than one compartment
• Arthritis may later develop in other areas of the knee

Total Knee Replacement

Possible considerations include:

• Treats wider knee joint damage
• May be suitable for patients with multi-compartment arthritis
• May address deformity or broader joint wear
• Recovery may take longer
• As with any surgery, there are risks such as infection, stiffness, blood clots, implant-related issues, or need for future revision surgery

How Doctors Decide Between Partial and Total Knee Replacement

An orthopaedic assessment may include:

• Symptom history
• Physical examination
• Walking and alignment assessment
• Knee stability testing
• X-rays
• MRI or other imaging if needed
• Review of previous treatments

The decision is based on whether knee damage is localised or widespread, whether the ligaments are stable, and whether the patient’s symptoms match the imaging findings.

Questions to Ask Your Orthopaedic Surgeon

Patients may consider asking:

• Is my knee damage limited to one compartment?
• Am I suitable for partial knee replacement?
• Would total knee replacement be more appropriate for my condition?
• What are the risks of each option?
• What recovery timeline should I expect?
• Will I need physiotherapy after surgery?
• What activities should I avoid after surgery?
• How long may the implant last?
• What symptoms should urgent review after surgery prompt?