A partial knee replacement is a surgical procedure where only one part of a damaged knee is replaced with an artificial implant, called a prosthetic. This procedure is an alternative to total knee replacement for patients whose disease is limited to just one area of the knee. The areas that can be replaced include the inside (medial) part, the outside (lateral) part, or the kneecap part of the knee. Partial knee replacement is appropriate for patients with arthritis that is confined to a single compartment of the knee and is generally restricted to patients who are not morbidly obese (BMI greater than 40) . The surgery is not appropriate for patients with marked stiffness in the knee or for those with a significant angular deformity. Generally, a patient must have intact knee ligaments to be a candidate.

Partial knee replacement is widely recognized as a technically demanding surgery. However, it has several advantages over total knee replacement, including quicker recovery, less pain after surgery, less blood loss, and lower risk of infection and blood clots. Partial knee replacement will address the arthritis that is present in the particular compartment of the knee that is already affected. In addition, the knee is typically rebalanced by the procedure, which improves its stability. While rare, there is no guarantee that arthritis will not progress elsewhere in the knee. Should this occur, a surgical revision to a total knee replacement may be necessary. Compared to total knee replacement, partial knee replacement better preserves range of motion and knee function because it preserves healthy tissue and bone in the knee. For these reasons, patients tend to be more satisfied with partial knee replacement compared with total knee replacement.