The term total knee replacement sounds somewhat drastic. This operation would be better named a surface replacement of the knee. The remaining cartilage and approximately 5-10 mm of bone is removed from the ends of all of the bones: femur , tibia , and patella. Three artificial component surfaces are then fixed to the ends of these bones. The anterior cruciate ligament and sometimes the posterior cruciate ligament are removed when this surgery is performed. Much less bone is removed in a partial knee replacement (unicompartmental knee replacement , UKR).