Although not as common as total knee replacement, a partial (unicompartmental) knee replacement is an attractive alternative in appropriately selected patients. The designs of the partial knee replacement devices have improved over the years, but are still composed of a combination of metal and plastic prosthetic devices. The partial knee replacement also utilizes smaller, minimally invasive incisions to perform the procedure. The partial knee replacement is used to replace a single part of the three compartments of the knee: the medial (inner) part, the lateral (outer) part, or the patellofemoral (kneecap) part.