Unicompartmental/Partial Knee Replacement

What is Unicompartmental/Partial Knee Replacement?

The knee joint has three compartments:

• Medial compartment: The inner portion of the knee
• Lateral compartment: The outer portion of the knee
• Patellofemoral compartment: The area where the kneecap meets the femur

Unicompartmental knee replacement, also known as a partial knee replacement, is a surgical procedure in which only the damaged compartment is treated. The damaged portions of the bone and cartilage are removed and replaced with prosthetic components.

Unlike total knee replacement, which replaces the damaged surfaces throughout the knee, partial knee replacement preserves the healthy portions of the joint when appropriate.

The procedure is designed to relieve pain, improve knee function, and preserve as much of the patient's natural knee as possible.

When is Unicompartmental/Partial Knee Replacement Recommended?

Partial knee replacement may be considered when arthritis or other joint damage is primarily limited to one compartment of the knee and nonsurgical treatments have not provided adequate relief.

Potential indications include:

• Osteoarthritis affecting primarily one compartment of the knee
• Significant cartilage loss limited to one compartment
• Persistent knee pain that interferes with daily activities
• Knee stiffness or reduced mobility
• Symptoms that have not improved adequately with nonsurgical treatment

Nonsurgical treatments may include medications, physical therapy, activity modification, injections, weight management, and other treatments recommended by your physician.

The decision to perform partial knee replacement depends on several factors, including the location and severity of arthritis, the condition of the remaining knee compartments, ligament stability, knee alignment, range of motion, overall health, and activity level.

How is Unicompartmental/Partial Knee Replacement Diagnosed?

Your surgeon will perform a comprehensive evaluation to determine whether partial knee replacement is appropriate.

The evaluation may include:

• Medical history: Your symptoms, previous injuries, surgeries, treatments, and overall health are reviewed.
• Physical examination: Your surgeon evaluates knee alignment, stability, range of motion, swelling, tenderness, and pain.
• X-rays: Weight-bearing X-rays can help identify narrowing of the joint space and other signs of arthritis.
• Additional imaging: MRI, CT, or other imaging studies may be recommended when additional information is needed to evaluate the knee.

Your surgeon will also assess the condition of the other compartments and the ligaments of the knee before recommending partial knee replacement.

How is Unicompartmental/Partial Knee Replacement Performed?

Unicompartmental knee replacement is performed under anesthesia. The specific surgical technique varies according to the affected compartment, the patient's anatomy, and the implant system being used.

During the procedure:

• The surgeon makes an incision over the knee to access the affected compartment.
• The damaged cartilage and a small amount of underlying bone are removed from the affected surfaces.
• The bone surfaces are prepared to receive the prosthetic components.
• The femoral and tibial components are positioned in the affected compartment.
• A plastic bearing is placed between the metal components to allow smooth movement of the knee.
• The surgeon evaluates the alignment, stability, and range of motion of the knee.
• The incision is closed, and a sterile dressing is applied.

Only the damaged compartment is treated, while the healthy portions of the knee are preserved.

What Can I Expect After Unicompartment/Partial Knee Replacement?

Recovery following partial knee replacement varies from patient to patient. Your surgeon will provide individualized postoperative instructions based on your procedure and overall health.

Postoperative care may include:

• Temporary use of a walker, cane, or crutches
• Pain and swelling management with prescribed medications and other recommended measures
• Physical therapy and prescribed exercises
• Gradually increasing weight-bearing and activity as directed
• Caring for the surgical incision as instructed
• Attending follow-up appointments
• Gradually returning to normal daily activities

Physical therapy can help restore knee strength, flexibility, range of motion, balance, and function.

Your surgeon will determine when it is safe to return to driving, work, exercise, sports, and other activities.

What are the Advantages of Unicompartmental/Partial Knee Replacement?

For appropriately selected patients, partial knee replacement may offer several potential advantages compared with total knee replacement.

These may include:

• Smaller surgical incision
• Preservation of healthy bone and cartilage
• Preservation of more of the patient's natural knee
• Potentially less blood loss
• Less postoperative pain in some patients
• Faster rehabilitation in appropriately selected patients
• Preservation of knee motion
• A knee that may feel more natural during movement

The potential benefits vary from patient to patient. Partial knee replacement is not appropriate for everyone with knee arthritis, and your surgeon will determine which procedure is most suitable for your condition.

What are the Risks and Complications of Unicompartmental/Partial Knee Replacement?

Although unicompartmental knee replacement is generally considered safe, it is still a surgical procedure and carries potential risks.

Possible complications include:

• Infection
• Blood clots, including deep vein thrombosis
• Bleeding
• Injury to nerves or blood vessels
• Knee stiffness
• Persistent pain
• Implant wear or loosening
• Fracture
• Instability
• Progression of arthritis in another compartment of the knee
• Need for additional surgery, including conversion to total knee replacement

Your individual risk depends on factors such as your age, overall health, knee condition, activity level, and the complexity of the procedure. Your surgeon will discuss the potential risks and benefits with you before surgery.