**2. Risk factors**

the race and ethnicity. Asians have a very low incidence of deep-vein thrombosis due to the preferred vegetarian diet, low prevalence of obesity, hyperlipidemia, and Factor V Leiden mutation. Several meta-analysis studies have shown similar results of low DVT incidence in Asians [2]. Operating surgeon has to minimize the risk of occurrence of this complication and its associated morbidity and mortality. Surgeon's choice of VTE prophylaxis should be based on a balance between safety and efficacy of a particular anticoagulant, with risk stratification of VTE or bleeding. Virchow's triad of events—stasis, vascular endothelial injury, and hypercoagulability, increases the risk of deep-vein thrombosis (DVT). Patients who fulfill two of the three criteria are considered to be high-risk group. Most of the patients undergoing TKA are considered to be at high risk for DVT for the high incidence of endothelial injury during the surgery and the relative stasis during the postoperative period. Well's criteria help us to

stratify risk in these patients (**Figure 1**).

42 Primary Total Knee Arthroplasty

**Figure 1.** Well's criteria for DVT risk stratification.

The risk factors for the development of DVT can be modifiable or nonmodifiable factors.

Modifiable factors include


Nonmodifiable risk factors include the genetic factors which cause thrombophilic disorders. Protein C, protein S, and antithrombin deficiencies, Factor V Leiden mutation, and increased level of factor V, VII, VIII, IX, XI and von Willebrand factor are a few of the conditions that add up the risk of DVT.

Triggering factors are incidental situations which put patients into high risk of developing DVT, which cannot be avoided but can be tided over.

