Knees for You Guide to Knee Replacement

Unicompartmental (Partial) Knees

In some patients, disease affecting the knee joint is limited to one side (or compartment) of the knee. In the past, a total knee replacement meant that although the damaged side was being replaced, so was the other side, which was not affected by the disease. With the introduction of unicompartmental (or half-knee) replacement systems, it became possible for surgeons to be more conservative in their treatment of selected patients, and to only replace the damaged compartment within the knee. This type of procedure is considered more conservative than total knee replacement, since the unaffected side of the knee is left in place. Moreover, new operative techniques allow this procedure to be carried out through a much smaller incision - so-called minimally invasive techniques - which result in less tissue damage and faster post-operative recovery.

A partial knee replacement -- also called a unicompartmental knee replacement -- involves putting an implant on just one side of the knee, rather than over the entire surface of the knee joint. Think of the knee as having three compartments: an inside, outside, and a front compartment for the kneecap. Most frequently, it is the inside compartment that becomes arthritic. A unicompartmental knee replacement is done if part of the knee joint is damaged by arthritis and the other compartments have healthy, normal cartilage.

By retaining undamaged parts of the knee, the joint may bend better and function more naturally.

In a healthy knee, the meniscus serves as a shock absorber between the ends of the bones. The implant features an artificial meniscal bearing designed to glide freely throughout the knee's range of motion, more closely replicating normal movement. The free floating nature of the device also improves durability of the implant.