How Many Types of Knee Prostheses Are There? What Are the Differences and Which Surgical Option Is Right for Knee Osteoarthritis?

Knee replacement surgery is one of the treatment options for severe knee osteoarthritis that significantly affects daily life, allowing patients to regain movement close to normal. How many types of knee prostheses are there? How are they different? And which type is suitable for which group of patients with knee osteoarthritis? You can find the answers to these questions in this article.

Key Takeaways

• Knee replacement surgery is currently the most effective treatment for knee osteoarthritis. It helps patients regain mobility close to normal.
• How many types of knee prostheses are there? There are two types:
• Total Knee Arthroplasty (TKA) and Unicompartmental Knee Arthroplasty (UKA).
• How to choose the right surgical option and which type is suitable for whom.

How Many Types of Knee Prostheses Are There and How Are They Different?

At present, there are two main types of knee prostheses: total knee surface replacement and partial knee surface replacement.

Total Knee Arthroplasty Prosthesis (TKA)

A total knee prosthesis is designed to replace the entire knee joint surface. This procedure involves removing all deteriorated joint surfaces, including the distal femur and proximal tibia, and in some cases, replacing the patellar surface as well.

The artificial joint surfaces are made from medical-grade synthetic materials that are safe for the human body, such as titanium alloys, cobalt-chromium alloys, high-quality polyethylene, and ceramics. These materials replace the worn joint surfaces and are durable and resistant to wear.

Main Components of a Total Knee Prosthesis (3 parts)

1. Femoral Component

• Made from cobalt-chromium alloy
• Large in size, similar to the patient’s original knee or approximately the width of the patient’s palm
• Curved in shape to mimic the natural anatomy of the distal femur, allowing proper knee bending
• Fitted over the cut distal femur to form the upper joint surface

There are various design options that produce different outcomes, such as:

• Cruciate-retaining designs
• Cruciate-sacrificing designs

Cruciate-retaining designs reduce bone removal at the distal femur and lower the risk of femoral fracture. National registry studies, such as those from Australia, have shown that cruciate-retaining knee prostheses have lower revision rates than cruciate-sacrificing designs.

Additionally, there are designs that adjust component width to better match the patient’s knee anatomy, as well as special coatings such as ceramic to increase smoothness and strength, reducing wear. Ongoing development focuses on improving prosthesis performance to better replicate natural knee movement and enhance postoperative function.

2. Tibial Component

This component is similar in size to the patient’s original knee and consists of two parts:

1. Metal baseplate

• Made from cobalt-chromium alloy or titanium alloy
• Designed with a stem that anchors into the bone cavity

2. Weight-bearing insert

• Made from high-quality polyethylene
• Supports body weight and reduces wear during movement between the upper and lower knee components

The tibial base varies in design and material, including base shape, metal type, and thickness. These factors affect force distribution on the remaining bone and influence prosthesis durability.

The polyethylene insert also varies in material composition and manufacturing process, which impacts wear resistance.

Like the femoral component, tibial components have a wide range of designs and continue to be developed.

3. Patellar Component

• Made from high-quality polyethylene
• Replaces the patellar surface
• Design variations exist

In most cases, the patellar surface is cut and replaced with a polyethylene component. However, in some cases, the surgeon may decide not to replace the patellar surface.

Because this surgery replaces the entire joint surface, it is suitable for patients with advanced osteoarthritis, severe joint degeneration, and significant deformity. Bow-leg or knock-knee deformities can be corrected.

Reported data show that over 90% of total knee prostheses last more than 15 years after surgery.

Unicompartmental Knee Arthroplasty (UKA)

A partial knee prosthesis is designed to replace only the knee compartment that is damaged in the early stage of the disease. Most commonly, this involves the inner (medial) compartment of the distal femur and proximal tibia. The patella is not replaced.

The artificial joint surfaces are made from medical-grade synthetic materials such as cobalt-chromium alloy, high-quality polyethylene, and ceramics, which safely replace the damaged joint surfaces and provide durable wear resistance.

Main Components of a Partial Knee Prosthesis (2 parts)

1. Femoral Component

• Small in size, approximately the size of the patient’s thumb
• Made from cobalt-chromium alloy
• Curved to replicate the natural anatomy of the distal femur
• Allows knee movement that closely resembles natural motion
• Fitted over the distal femur with small fixation pegs

Special coatings such as ceramic may be applied to enhance smoothness, strength, and reduce wear.

2. Tibial Component

Consists of two parts:

1. Metal baseplate

• Made from cobalt-chromium alloy
• Small in size, approximately the patient’s thumb
• Flat design with small fixation points

2. Weight-bearing insert

• Made from high-quality polyethylene
• Supports weight and reduces wear during knee movement

This component comes in two designs:

• Mobile-bearing insert
• Fixed-bearing insert

Each has advantages and disadvantages. National-level studies show no significant difference in revision rates between the two designs.

Because this procedure replaces only part of the joint, it is suitable for patients with mild osteoarthritis, minimal deformity, and has a shorter lifespan than total knee replacement. Degeneration may still occur in the unreplaced compartments.

This surgery requires extremely high precision due to the small implant size. Even minor misalignment can significantly increase the risk of revision surgery. Surgical accuracy can be improved with robot-assisted surgery.

Both types of knee prostheses are generally fixed to existing bone using bone cement, which is similar to the white filling material used by dentists. This method provides strong fixation and is considered the gold standard in current knee replacement surgery.

There are also cementless knee prostheses, which use specially designed metal surfaces that allow bone to grow into the implant. These are more expensive and are believed to offer increased durability.

Choosing the Right Knee Prosthesis for Better Stability and Confidence in Walking

Knee replacement surgery is currently the most effective treatment for severe knee osteoarthritis. It reduces pain and improves quality of life. Proper postoperative care and strengthening of the muscles around the knee can extend implant longevity and improve function, allowing patients to move forward with confidence.

At the Joint Care Center, Praram 9 Hospital, we provide specialized care by orthopedic specialists, helping patients regain stable and independent mobility as quickly as possible.

For More Information

• Facebook : Praram 9 hospital
• Line : @Praram9Hospital
• Tel. 1270

Frequently Asked Questions About Knee Replacement Surgery

Can knee replacement surgery be performed on both knees at the same time?

Yes, knee replacement surgery can be performed on both knees simultaneously. However, the decision depends on the physician’s evaluation and the patient’s preference.

How many days after knee replacement surgery can a patient walk?

Most patients can begin weight-bearing and walking with support within 1 day after surgery.

References

Institute for Quality and Efficiency in Health Care (IQWiG). (2024, May 15). Osteoarthritis of the knee: Learn more – What are the different types of artificial knee joints? In InformedHealth.org. https://www.ncbi.nlm.nih.gov/books/NBK544988/

Knee Replacement Implants. (n.d.). orthoinfo. https://orthoinfo.aaos.org/en/treatment/knee-replacement-implants/

Monte, M. (2023, August 24). Knee replacement options: What are some types and considerations? MedicalNewsToday. https://www.medicalnewstoday.com/articles/types-of-knee-replacement-options

Chaiyakit P, Ompornuwat K, Hongku N, Janphaung P. Stress shielding in the proximal tibia after total knee arthroplasty: A finite element analysis of 2- and 4-mm thick tibia prosthesis models Vajira Medical Journal: journal of Urban Medicine Vol.66 No.6 Nov-dec 2022. https://he02.tci-thaijo.org/index.php/VMED/article/view/259206