 In patients undergoing primary total knee arthroplasty, perioperative anemia is highly prevalent. In a systematic review, preoperative anemia was found in 24 - 9 and postoperative anemia in 51 - 10. Perioperative anemia was associated with a blood transfusion rate of 45 - 25, postoperative infections, poorer physical functioning and recovery, and increased length of hospital stay LOS and mortality. Although the best transfusion trigger in elective patients remains unknown, restrictive transfusion protocols are recommended and avoidance of blood transfusion if possible. 