Unicompartmental Knee Arthroplasty as Treatment for Osteoarthritis

What is Osteoarthritis?

With osteoarthritis, the cartilage that protects the bones of the joint and allows for fluid movement of the joint wears down, causing pain. 

Depending on the extent of the condition, the cartilage can be worn out completely, causing the bones of the joint to rub together. In such cases, you might hear the term “bone on bone,” meaning that the cartilage has completely degenerated, and there is no longer a space between the bones in the joint. 

Osteoarthritis commonly occurs in the knees, hips, and spine.

Anatomy of Knee Joint

The knee joint is where your thigh bone, known as the femur, meets your shin bone, known as the tibia. There is also the kneecap, known as the patella, that sits and glides on the femur. Sitting on the ends of the femur and tibia is a tissue called cartilage, which protects your joints and helps with fluid movement of the joint.

The knee joint is divided into three separate areas, also known as compartments. These include the medial, lateral, and patellofemoral compartments. The medial compartment is found on the inside part of the knee, while the lateral compartment is found on the outside part of the knee. 

The patellofemoral compartment is found in the front of the knee, between the patella and the femur. 

Osteoarthritis can develop in any one or a combination of the three compartments. Oftentimes, the medial compartment is the region where patients experience pain, as this is most often the area that develops osteoarthritis first.

What Are the Symptoms of Osteoarthritis?

Symptoms of osteoarthritis typically develop gradually and worsen over time. Typically, the symptoms will worsen with use and may be alleviated with rest. Symptoms may include:

• Pain, which worsens with activity
• Stiffness
• Grinding
• Swelling
• Decreased range of motion

Treatment Options for Knee Osteoarthritis

Depending upon the severity of your condition, there are a variety of treatment options available for knee osteoarthritis. 

Non-surgical treatments include things like over-the-counter medications, such as Advil and Tylenol, anti-inflammatory creams, and gel or steroid injections.

Surgical treatments include knee replacements. These include total and partial knee replacements that could potentially be utilized. A detailed discussion with your orthopedic surgeon can help you determine which method of treatment is right for you.

What Is a Unicompartmental Knee Arthroplasty?

A unicompartmental knee arthroplasty, or partial knee replacement, is a knee replacement aimed at one specific compartment rather than replacing the entire knee. In certain patients, osteoarthritis may develop in only one compartment of the knee and can be corrected as such. 

In this procedure, the surgeon will make an incision on the front of your knee, remove the damaged bone and cartilage, and insert a metal implant on the affected side of the femur and tibia, as well as a spacer between the two metal components. 

The combination of these components allows the surgeon to artificially restore the normal space between the two bones, which is normally formed by cartilage. This will restore smooth movement of the knee and reduction of pain.

Robot-Assisted Unicompartmental Knee Arthroplasty

New progressions in unicompartmental knee arthroplasty have allowed for the use of robotic assistance during the surgery. There are multiple systems that currently have FDA approval. 

One such system allows the surgeon to generate real-time models of your knee and test different-sized components within the accompanying software. Other systems require a preoperative CT scan for mapping and planning purposes. 

Another system, which is currently in the process of obtaining FDA approval, can compensate for surgeon hand placement for precise location and placement of surgical guides. With this technology, surgeons have the capability of fine-tuning the surgery and removal of damaged tissue to within half a millimeter of precision. 

This increased precision can allow for more accurate alignment and balancing of the knee, contributing to improved function and results. Additionally, patients may experience shorter recovery times as a result of the robotic assistance.

The Advantages and Disadvantages of Unicompartmental Knee Arthroplasty

Unicompartmental knee arthroplasties offer some potential benefits to patients who qualify compared to traditional total knee arthroplasties. As the damaged bone and cartilage is only being replaced on the affected side of the knee, you maintain your original tissue on the healthy side of your knee. 

Additionally, you may experience less postoperative pain and a quicker recovery due to the decreased removal of native structures. 

A potential disadvantage of unicompartmental knee arthroplasty is the possibility of additional surgery in the future. If your arthritis were to develop in other compartments of the knee, you may require a conversion to a total knee arthroplasty from your unicompartmental arthroplasty. However, the rates of such conversions are low. 

Book Your Appointment Today

Our orthopedic surgeons at OrthoNeuro can provide more specific details regarding your qualification for a unicompartmental knee arthroplasty or total knee arthroplasty based on your current condition. Book your appointment today at one of our locations in Columbus, Ohio!

References

• Center for Disease Control and Prevention. Osteoarthritis (OA). (https://www.cdc.gov/arthritis/basics/osteoarthritis.htm#:~:text=Osteoarthritis%20(OA)%20is%20the%20most,underlying%20bone%20begins%20to%20change.)
• American Academy of Orthopedic Surgeons. Unicompartmental (Partial) Knee Replacement. (https://orthoinfo.aaos.org/en/treatment/unicompartmental-knee-replacement/)
• National Institute of Arthritis and Musculoskeletal and Skin Diseases. Osteoarthritis. (https://www.niams.nih.gov/health-topics/osteoarthritis)
• Luo TD, Hubbard JB. Arthroplasty Knee Unicompartmental. [Updated 2022 Jul 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538267/
• Lonner, Jess H. MD; Klement, Mitchell R. MD. Robotic-assisted Medial Unicompartmental Knee Arthroplasty: Options and Outcomes. Journal of the American Academy of Orthopaedic Surgeons 27(5):p e207-e214, March 1, 2019. | DOI: 10.5435/JAAOS-D-17-00710

Medically Reviewed by Mark Gittins, DO