Unicompartmental Arthroplasty


Arthritis affects the inner compartment of the knee (arrow). A Unicompartmental knee replacement has been used as the other compartment of the knee were not affected by arthritis.

If arthritis is confined to one compartment of the knee joint, and non-surgical treatment has been ineffective, resurfacing the damaged compartment of the knee can relieve knee pain very effectively. This procedure is termed a “unicompartmental arthroplasty” and involves implanting a metal and plastic bearing into the arthritic compartment of the knee.

There are specific indications for this operation, where arthritis is confined to one compartment of the knee (although a degree of wear behind the kneecap does not appear to matter). Symptoms must be localised to the affected compartment of the knee and there should be good range of knee movement. The operation is most commonly performed for arthritis of the medial compartment of the knee, although it can also be effective for localised patello-femoral compartment arthritis and more rarely isolated arthritis in the lateral compartment of the knee.

Unicompartmental arthroplasty is still joint replacement surgery and there are risks of complications, including infection, knee stiffness, loosening and mechanical failure of the implants, and persistent knee pain. There is a risk of failure due to arthritis developing in the other compartments of the knee, causing a recurrence of knee pain. Under these circumstances, a re-do operation may be required to remove the implant and perform a total knee replacement.