Unicompartmental Knee Replacement

Unicompartmental knee arthroplasty, also known as partial knee replacement, involves replacing only the damaged compartment of the knee joint rather than the entire joint, which is the case in total knee arthroplasty. The knee joint is composed of three compartments: the medial (inner) compartment, the lateral (outer) compartment, and the patellofemoral (front) compartment. Unicompartmental knee arthroplasty is indicated when only one of these compartments is damaged or diseased.

Indications for Unicompartmental Knee Arthroplasty:

1. Isolated Compartmental Osteoarthritis: The primary indication is osteoarthritis that is limited to one compartment of the knee, typically the medial compartment. The remaining compartments must be well preserved prior to and during surgery for unicompartental knee arthroplasty to be successful.
2. Intact Ligaments: Cruciate ligaments, especially the anterior cruciate ligament (ACL), should be functional and intact.
3. Limited Inflammation: The inflammatory changes in the synovium should be minimal. This means patients with inflammatory arthritis, like rheumatoid arthritis, are not eligible.
4. Preserved Range of Motion: The patient should ideally have a reasonably good range of motion preoperatively.
5. Absence of Significant Axial Deformity: Mild varus or valgus deformity (bowlegged or knock kneed) is acceptable, but severe deformities are a contraindication to partial knee replacements.

Advantages of Unicompartmental Knee Arthroplasty:

1. Less Bone Resection: Only the affected compartment is resurfaced, preserving more of the patient’s natural bone.
2. Shorter Recovery Time:  Due to the smaller incision and preservation of more natural structures, the postoperative recovery is typically quicker than with total knee replacement.
3. Reduced Blood Loss:  The surgery is less invasive, leading to less blood loss during the operation.
4. Better Knee Kinematics: The natural motion of the knee is better preserved, often leading to a more “natural” feeling knee after surgery.
5. Reduced Hospital Stay: This surgery is routinely performed as a same day, outpatient procedure, so patients can go home sooner after a partial knee replacement than after a total replacement.
6. Possibility of Future Surgeries: If the other compartments of the knee become arthritic in the future, a total knee replacement can still be an option.

Despite its advantages, unicompartmental knee arthroplasty is not suitable for everyone. It’s crucial for candidates to be appropriately selected. When done for the right indications, partial knee replacements can have excellent outcomes and provide significant relief from arthritis pain. At Total Orthopedics and Sports Medicine we have specialists trained in performing unicompartmental arthroplasty who can determine if this procedure is indicated for your joint replacement.