Answer:
Total knee replacement is a medical surgery that helps in removing the defective knee and replaced the knee with the synthetic material. Any defects in the knee can be corrected by this surgery.
Autologous transfusion is the type of blood transfusion in which the blood is taken from the another part of the patient's body and then reinsert in the same body. The total knee replacement might require autologous tranfusion. The statement made by the nurse that she needs to donate blood around 4 to 6 weeks before the surgery indicates autologous transfusion.