Joint replacement is removing damaged joint cartilage and underlying bone and replacing it with metal and plastic.
Tibiofemoral partial knee replacement, replacing one compartment of the joint.
Model bones to show the components of a total knee replacement. In fact this only shows replacement of the tibiofemoral joints, but the patellofemoral are generally also replaced.
Joint replacement in the knee
In the knee the surgeon can replace the whole joint, or part of the joint.
Lessons Learned From Managing a Prospective, Private Practice Joint Replacement Registry: A 25-year Experience. Carothers JT, White RE, Tripuraneni KR, Hattab MW and Archibeck MJ. Clin Orthop Relat Res. 2013 Feb; 471(2): 537–543.