Total hemoglobin (Hb) loss, drain output, hidden blood loss (HBL), calculated total blood loss (TBL) on the first postoperative day (POD1) and one week postoperatively (POD7), postoperative flexion angle at one week and discharge, and incidence of postoperative deep venous thrombosis (DVT) were assessed. The gene discussed is GSTM1; the disease is deep vein thrombosis.