The purpose of the study is to evaluate the efficacy and safety of SHR-2004 in preventing venous thromboembolism after elective unilateral total knee arthroplasty

Inclusion Criteria:

1. Understand the research procedures and methods, volunteer to participate in the study, and sign the informed consent
2. Scheduled to undergo elective unilateral total knee arthroplayts (TKA)
3. Male or female(≥ 40 years old and < 80 years old)

Exclusion Criteria:

1. Unable to receive CT angiography of both lower limbs;

2. Malignant tumor within one year of the screening ;

3. History of venous thromboembolism;

4. Myocardial infarction, transient ischemic attack or ischemic stroke occurred within 6 months of the screening;

5. Any medical history that may increase the risk of bleeding or any conditions that the investigator considers to increase the risk of bleeding

6. Any of the laboratory test indicators meets the following criteria:

   ①estimated Glomerular Filtration Rate < 60 mL/min/1.73m2 ;

   ②Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >3 times the upper limit of normal value (ULN);

   ③total bilirubin was > 2 times, etc

7. History of drug abuse;

8. Pregnant or lactating women