Normally the surgery is carried out under tourniquet hence the bleeding is minimum during surgery. After the surgery usually there is some ooze from the surgical site, but if your pre operation blood level is adequate, you may not need any transfusion.

Only if one is getting both knees operated in the same sitting, we usually keep two bottles of blood reserved. It is always advisable to arrange for 2 healthy donors from your family or friends for donation prior to surgery, to assure that good quality of blood is available after the surgery.

The blood which will be given to you is always checked for its purity and it is seen that it's properly tested as per Government regulations.

If your haemoglobin level is adequate and if you are under 65 years , you may considered for auto-transfusion if you so desire. In auto-transfusion, patient's own blood is collected prior to operation, and is given back to the patient after the operation. The obvious advantage of this technique is no risk of any transfusion related reactions.