This study showed that for knee arthroscopy surgery, the incidence of DVT in patients without anticoagulation was 7.4%, which is very close to the result of Delis et al. , although the incidence was not as high as major operations such as arthroplasty , but its importance cannot be ignored. In contrast, the incidence of DVT in the anticoagulation patients group was 7.5%, which indicated that the use of LMWH may not reduce the probability of DVT in patients within three days after knee arthroscopic surgery. Kessler  noted that it is suitable to use LMWH for five to seven days after arthroscopic knee surgery. Another randomized controlled trial has revealed that prophylaxis should last seven to ten days , as other studies have shown poor results for short-term preventive treatment of only three to six days [18, 19]. Although LMWH did not increase the risk of perioperative bleeding, it was not a protective factor to prevent the formation of postoperative DVT in three days. In some previous studies, it was shown that thromboprophylaxis was not recommended after arthroscopic surgery [20–22]. A recent systematic review suggested that they against routine use of thromboprophylaxis even after anterior cruciate ligament reconstruction surgery . In arthroplasty operations, the use of LMWH has become an industry guideline , however, among patients undergoing arthroscopic surgery, a short-term use of LMWH is not recommended to prevent the formation of DVT in patients without risk factors according to our study.
D-dimer as a fibrin degradation product, generally assumed has a tendency to decline to normal level within three to ten days after tissue injury [25, 26], and has a high sensitivity for predicting the formation of postoperative DVT . Although D-dimer is affected by pregnancy, trauma, tumor and surgery [28, 29], this study excluded possible influencing factors except for surgery, we tried our best to minimize its effects. D-dimer is a sensitive but non-specific marker of DVT, so the positive result of D-dimer cannot be used for diagnosis, on the contrary, the possibility of thrombosis can be excluded when D- dimer is negative [30, 31]. Our results also demonstrated that for every unit increase in D-dimer, the probability of patients suffering from DVT increased by 3.7 times, so anticoagulation is necessary for patients with high D-dimer after knee arthroscopic surgery. Meanwhile, D-dimer provides a characteristic of quick and convenient. It can also be used as a routine examination to screen the formation of DVT in hospitals without ultrasound or venography, and unnecessary examination can be avoided for some low-risk patients.
The incidence of non-symptomatic DVT is very high (19/21, 90.5%), which was similar to those of sun et al. , so adequate attention should be paid to the latent DVT, and it is not reliable to diagnose the occurrence of DVT solely by clinical symptoms. At present, there are more and more diagnostic measures for thrombosis. Color doppler ultrasound as the preferred detection method has the advantages of quickness, convenience, non-invasiveness, and radiation-free, and has relatively high sensitivity and accuracy [33–35]. In this study, a high incidence of DVT was detected by color doppler ultrasound 3 days after surgery. Therefore, it is suggested that early ultrasound examination is necessary for each patient with increased D-dimer level after knee arthroscopic surgery.