Partial Knee Replacement (PKR), also known as Unicompartmental Knee Replacement (UKR), is a surgical procedure used when arthritis or other damage is mainly limited to one compartment of the knee.
The knee has three main compartments: the medial compartment on the inner side, the lateral compartment on the outer side, and the patellofemoral compartment between the kneecap and thighbone. In a partial knee replacement, the surgeon replaces only the damaged compartment rather than replacing the surfaces of the entire knee.
The most common reason for partial knee replacement is osteoarthritis affecting a single compartment of the knee, particularly the medial compartment. The damaged cartilage and underlying bone surfaces are removed and replaced with artificial components designed to restore a smoother joint surface.
Unlike a total knee replacement, the healthy compartments of the knee are preserved. Depending on the patient's anatomy and condition, important natural structures such as the remaining cartilage, ligaments and other healthy joint surfaces may be retained.
During surgery, the surgeon prepares the damaged area of the femur and tibia and places metal components with a medical-grade plastic bearing between them. The implant allows the treated part of the knee to move more smoothly while preserving the unaffected portions of the joint.
Partial knee replacement is generally considered when the damage is sufficiently localized and the remaining knee structures are suitable for the procedure. The surgeon evaluates symptoms, physical examination, X-rays or other imaging, ligament stability and the condition of the other knee compartments before deciding whether partial or total replacement is appropriate.
In some cases, the final decision between partial and total knee replacement may only be made after the surgeon directly assesses the condition of the joint during surgery.
The aim is not simply to replace a damaged portion of the knee but to reduce pain, preserve as much of the patient's natural knee as appropriate, and restore useful movement and function.