Unicondylar knee arthroplasty, also known as partial or unicompartmental knee replacement, is a less invasive alternative to a total knee arthroplasty. Partial knee arthroplasty is designed to replace only the portion of the knee that has been damaged by arthritis, leaving the healthier areas intact. Partial knee replacement allows patients to benefit from less scarring, shorter recovery time and a fuller range of motion.

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Candidates for a Unicondylar Arthroplasty

Although most candidates for this procedure are over the age of 55, this procedure may be performed on younger patients who are relatively incapacitated by their knee damage. Good candidates include patients who do not suffer from rheumatoid arthritis, whose arthritis is localized to one specific area of the knee, and whose ligaments are in good condition.

To determine whether a unicondylar knee arthroplasty is the best course of treatment for a particular patient, the doctor performs a physical examination to evaluate precisely which area of the knee is producing the pain. Imaging tests will also be conducted, including X-rays and MRI scans to detect the precise location of cartilage damage and its severity.

The Unicondylar Arthroplasty Procedure

Unicondylar knee arthroplasty may be performed under either general or spinal anesthesia. The surgery generally takes 1 to 2 hours to complete. The surgeon makes an incision at the front of the knee close to the affected area. This incision provides the surgeon with the opportunity to assess the structures of the knee, to ensure that the nearby ligaments are healthy and that the damage is confined to one specific area. If arthritis is present in multiple areas of the knee, total knee arthroplasty may have to be substituted for partial knee replacement.

Assuming that the damage to the knee joint is confined to one region, the unicondylar replacement will proceed. The surgeon will excise small pieces of cartilage and bone from the affected portions of the femur (thigh bone) and tibia (the larger bone of the lower leg). The segments of bone are replaced with metal prosthetics and fixed in place with cement. The metal implants at the ends of the bones are separated by a plastic insert that allows for smooth, fluid motion of the joint after surgery.

Recovery from a Unicondylar Arthroplasty

Recovery from a partial knee replacement is normally shorter and more comfortable than recovery from of a total knee arthroplasty. Unicondylar knee replacement is a less invasive procedure, performed through a smaller incision. However, even a partial knee replacement typically requires a hospital stay of 1 to 3 days.

Most patients require the use of an assistive device such as crutches or a walker for the first week or two following the procedure to prevent putting too much stress on the knee as it heals. Physical therapy is important as it can help the knee to regain strength and flexibility. After a partial knee replacement, many patients fully recover within 6 weeks and are able to resume their usual activities, including low impact sports.

Risks of a Unicondylar Arthroplasty

While partial knee arthroplasty is considered a safe procedure, all surgeries carry some risk. The risks associated with a unicondylar knee replacement include infection, development of blood clots, damage to blood vessels or nerves and lingering pain in the knee. In general, however, because unicondylar knee replacement is a shorter and less invasive procedure than a total knee arthroplasty, it carries a smaller risk of complications.