Unicompartmental or “partial” knee arthroplasty is much less invasive than a total knee replacement but is designed to treat knee arthritis that is confined to only one part of the knee. A unicompartmental knee arthroplasty can be thought of as a “half” knee replacement. It does not require the cutting of the anterior or posterior cruciate ligaments, as is required in most total knee replacements, and involves less bone removal. A unicompartmental knee works very well in patients who have arthritis in only one “half” of the knee and is an excellent option in younger patient.