Objective:To investigate the factors for and prevention of muscular calf vein thrombosis (MCVT) after unilateral total knee arthroplasty (TKA).Methods:Between January 2018 and October 2020, 551 patients were admitted to Department of Orthopedics, The First Affiliated Hospital to Zhengzhou University for unilateral TKA. They were 187 males and 364 females, aged from 32 to 90 years (average, 64.6 years) and with 234 left and 317 right knees affected. They were assigned into a MCVT group ( n=77) and a non-MCVT group ( n=474) according to whether or not MCVT had happened at 7 days after operation. Recorded were the patients’ baseline information, tourniquet time, intraoperative blood loss, postoperative prothrombin time (PT), postoperative thrombin time (TT), postoperative fibrinogen (FIB), D-dimer, platelet count (PLT), postoperative bed time, knee society score (KSS), erythrocyte sedimentation rate (ESR) fall time, and C-reactive protein (CRP) fall time so as to analyze the risk factors for MCVT. Results:There were significant differences between the 2 groups in age [(66.8±7.0) versus (64.2±9.6) years], body mass index (BMI) [(28.7±2.2) versus (25.0±2.4) kg/m 2], smoking (20/57 versus 41/433), diabetes (56/21 versus 172/302), primary hypertension (45/32 versus 174/300), coronary heart disease (50/27 versus204/270), hyperlipidemia (33/44 versus 149/325), varicosity (50/27 versus 166/308), tourniquet time [(97.9±22.6) versus (83.1±10.6) min], intraoperative blood loss [(73.2±40.6) versus (62.4±11.5) mL], postoperative PT [(10.7±0.8) versus (11.9±1.0) s], TT [(15.2±1.3) versus (17.2±2.4) s], FIB [(3.7±0.8) versus (3.2±0.5) g/L], D-dimer [(1.1±1.0) versus (0.8±0.3) μg/L], PLT [(233.4±68.5) versus (178.5±27.8) 10 9/L], postoperative bed time [(17.3±2.6) versus (14.6±3.8) h], KSS [(3.32±0.7) versus (3.61±0.56) points], ESR fall time [(2.90±0.74) versus (1.55±0.64) d] and CRP fall time [(2.90±0.74) versus (1.55±0.64) d] (all P<0.05). Multivariate logistic regression analysis showed that old age (95% CI: 0.890 to 1.112, P=0.034), high BMI (95% CI: 1.012 to 1.214, P=0.046), diabetes (95% CI: 1.002 to 2.590, P=0.020), D-dimer (95% CI: 1.239 to 10.292, P=0.001) and postoperative PLT (95% CI: 1.012 to 1.112, P=0.014) were independent risk factors for MCVT. Reduced postoperative bed time (95% CI: 1.009 to 1.469, P=0.040) was a protective factor. Conclusions:As old age, high BMI, diabetes, and high postoperative levels of D-dimer and PLT may be independent risk factors for MCVT, patients with such characteristics should be alert to MCVT. Early ambulation should be encouraged in patients after unilateral TKA to reduce postoperative bed time for prevention of the disease.