Unicondylar Knee Replacement

What is Unicondylar Knee Replacement?

Unicondylar knee replacement, also known as partial knee replacement, is a surgical procedure where only a portion of the knee joint is replaced. This procedure is indicated for patients with localised arthritis affecting either the medial (inner) or lateral (outer) compartment of the knee. Unlike total knee replacement, which replaces the entire knee joint, unicondylar knee replacement targets only the affected compartment, preserving the healthy parts of the knee.

Anatomy of the Knee

The knee is made up of the femur (thighbone), tibia (shinbone) and patella (kneecap). The lower end of the femur meets the upper end of the tibia at the knee joint. A small disk of bone called the patella rests on a groove on the front side of the femoral end. The fibula, another bone of the lower leg, forms a joint with the shinbone. The bones are held together by protective tissues, ligaments, tendons, and muscles. Synovial fluid within the joint aids in the smooth movement of the bones over one another. The meniscus, a soft crescent-shaped area of cartilage between the femur and tibia, serves as a cushion and helps absorb shock during motion.

What are the Indications for Unicondylar Knee Replacement?

Localised Arthritis: Arthritis confined to either the medial or lateral compartment of the knee.
Intact Ligaments: The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) must be intact and functional.
Minimal Deformity: Patients with mild to moderate knee deformity, such as varus (bowlegged) or valgus (knock-kneed), that can be corrected.
Good Range of Motion: Patients should have relatively good range of motion in the knee joint.
Non-Responsive to Conservative Treatment: Failure to achieve pain relief and functional improvement with non-surgical treatments like medications, physical therapy, or injections.

What Does Preparation for Unicondylar Knee Replacement Involve?

In general, preparation for unicondylar knee replacement may include the following:

Comprehensive medical history, physical examination, and imaging studies (X-rays, MRI) to confirm the extent of the damage and suitability for unicondylar knee replacement.
Information about the procedure, risks, benefits, and rehabilitation process.
You should inform if you have allergies to medications, anaesthesia, or latex.
You should inform your doctor of any medications or supplements that you are taking.
You may be asked to avoid certain supplements or medications such as blood thinners that may affect blood clotting during surgery.
You should refrain from alcohol or tobacco for a defined period before surgery and after as it can hinder the healing process.
You should not consume any solids or liquids at least 8 hours prior to surgery.

What is the Procedure for Unicondylar Knee Replacement?

In general, procedure for unicondylar knee replacement may include the following steps:

Anaesthesia: The patient is given general or regional anaesthesia.
Incision: A small incision is made over the knee to access the affected compartment.
Exposure of the Joint: The joint is exposed, and the surgeon assesses the damage.
Preparation of Bone Surfaces: The damaged bone and cartilage are removed from the affected compartment.
Implantation of Prosthesis: The prosthetic components (usually made of metal and plastic) are implanted in the prepared bone surfaces. These include:
Femoral Component: Attached to the end of the femur.
Tibial Component: Attached to the top of the tibia.
Patellar Component: If needed, a patellar button may be used.
Alignment and Function Check: The components are checked for proper alignment, fit, and smooth movement.
Closure: The incision is closed with sutures or staples, and a sterile bandage is applied.

What Does Postoperative Care and Recovery for Unicondylar Knee Replacement Involve?

You will be taken to the recovery room and monitored for any complications. You will be given pain medication to keep you comfortable. Ice, compression, and elevation of the knee will help minimise swelling and pain. You may walk with the help of a walker or cane for the first 1-2 weeks after surgery. A physical therapist will advise you on an exercise program to follow for 4 to 6 months to help maintain range of motion and restore your strength. You may perform exercises such as walking, swimming and biking but high impact activities such as jogging should be avoided. You will be given specific instructions regarding activities. Eating a healthy diet and not smoking will promote healing.