What is unicompartmental (partial) knee arthroplasty?

What is knee arthritis?

Knee arthritis is an inflammatory condition characterized by the destruction of the joint’s structural elements, including the articular cartilage, menisci, and subchondral bones. The knee consists of three (3) compartments: the medial, the lateral, and the patellofemoral compartment.

Traditionally, treatment for knee arthritis—regardless of whether one or more parts of the joint were affected—was total knee arthroplasty, which involved replacing all joint surfaces. This often required sacrificing the anterior cruciate ligament and sometimes the posterior as well.

However, today, in cases where arthritis is limited to one or two of the three compartments (medial, lateral, patellofemoral), the patient may undergo replacement only of the damaged sections, preserving the healthy cartilage and avoiding cutting the anterior and/or posterior cruciate ligaments. This results in a more natural knee function and movement.

What are the preoperative procedures?

It is important to carefully select patients suitable for unicompartmental arthroplasty.

Medical history: The orthopedic surgeon will take a detailed history regarding the patient’s overall health and specific symptoms related to the affected knee.

Clinical examination: A thorough examination will follow to determine whether the pain is localized to one part of the knee or more, as well as to assess joint mobility and ligament stability.

Imaging: The patient must undergo specialized X-rays to evaluate the extent of damage. In some cases, further imaging, such as an MRI, may be required.

How is the surgery performed?

The surgery is performed through a small incision on the front of the knee. The surgeon will inspect the joint to confirm that arthritis is confined to one compartment and that the ligaments are intact.

Only the diseased bone and cartilage are removed, and the area is prepared for implant placement. Unlike total knee arthroplasty, all ligaments are preserved.

The damaged surfaces are typically replaced with metal components fixed to the bone using special biological cement. A strong plastic implant (made of polyethylene) is placed between the metal parts to enable smooth joint movement. These materials are durable, long-lasting, and biocompatible.

The wound is then closed.

Postoperative Care

After surgery, the patient is transferred to their room and begins knee mobilization immediately.

Usually, the hospital stay is only one (1) day, and the patient can bear weight on the leg immediately after surgery. For the first few days or weeks, crutches may be needed until the patient feels confident walking without them.

A physical therapist will assist with mobilization and provide instructions for range-of-motion and strengthening exercises.

What are the advantages of unicompartmental knee arthroplasty compared to total knee arthroplasty?

• Smaller incision
• Less soft tissue damage
• Less blood loss
• Less postoperative pain
• Fewer complications
• Shorter hospital stay (1 day)
• Immediate mobilization
• Faster return to daily activities
• Since the healthy cartilage and ligaments are preserved, postoperative joint movement closely resembles natural knee motion.

Are there any complications from the procedure?

Careful patient selection, thorough preoperative assessment and planning, and reduced surgical time minimize the risk of complications. A rare complication is deep vein thrombosis (DVT).