Postoperative anemia is a frequent complication after total knee arthroplasty, with an incidence of 87%. Iron supplementation is known to be effective in treatment and prevention of postoperative anemia. The investigators examined the effect of intravenous iron isomaltoside (Monofer®) administration on postoperative anemia and transfusion requirements in patients undergoing total knee arthroplasty.

Participants undergoing total knee arthroplasty will be randomly assigned to treatment group or control group. After main procedure of total knee arthroplasty, iron isomaltoside 1000 (Monofer®) or normal saline will be intravenously administered depending on the group assigned. The dose of iron isomaltoside will be determined based on patient's body weight using the manufacturer's recommendation. Serum hemoglobin, hematocrit, iron, ferritin, transferrin saturation, and phosphorus level will be checked at preoperative day, postoperative day 1, 7, and 30.

The primary outcome is the incidence of postoperative anemia at 30 days after surgery. Secondary outcomes included the incidence and amount of red blood cell transfusion during admission period, hospital length of stay, the incidence of surgical site infection, and quality of life during postoperative period.

Inclusion Criteria:

• Adult patients undergoing total knee arthroplasty

Exclusion Criteria:

• bilateral total knee arthroplasty
• hematochromatosis or hemosiderosis
• hemolytic anemia
• history of drug allergy
• liver cirrhosis or hepatitis
• systematic lupus erythematosus
• rheumatic arthritis
• allergic disease
• history of transfusion within one month from surgery
• parturient