## 4 Discussion  
In the present study, the risk of DVT was assessed for three groups of patients. In one of the groups, a regular reminder to the patient through vibration alarms of a foot band with motion sensor was used to increase the performance of the ankle pumping exercises, and the results confirmed a positive effect on peak venous blood flow and blood flow volume with Doppler after the surgery. Despite the absence of DVT incidence in this study, the Doppler examination provides additional evidence to support the contribution of the proposed approach in reducing the risk for DVT. Ankle pumping exercise is a proposed strategy to prevent the formation of DVT, but it is challenging to know the performance of the exercise, particularly when the patient is discharged to home. In the present study, the occurrence rate of stasis was 17.2% in the patient without exercise alarm for 11 days at home (group 1), while none of the patients with the same exercise and regular with exercise alarm had signs of stasis. A simple reminder with the alarm could reduce the incidence of stasis after TKR. Furthermore, regular reminders to the patients for exercise also significantly increased the peak blood velocity and flow volume in the vessels. These results demonstrate the effect of regular reminders to increase the effect of active ankle pumping exercises after TRK without supervision at home. Postoperative swelling and edema are common after TKR. Negative pressure drainage is typically used to remove stagnant tissue fluid. In addition to drainage, exercise has been suggested to reduce postsurgery edema [28]. In the present study, group 3 executed the exercise with reminders; hence, the execution rate of the exercise was certain. Because exercise helps reduce edema, the drainage volume is also reduced. In group 1, the execution of exercise was uncertain, and the drainage volume was greater than that in group 3. Although pneumatic compression has been reported to be beneficial in the acceleration of venous blood reflex, the effect of pneumatic compression on reducing edema remains uncertain. Hence, the drainage volume was more than that in group 3. Intermittent pneumatic compression, except for active ankle pumping exercises, is also a standard approach to prevent the formation of DVT [16; 17]. In the present study, despite the use of intermittent pneumatic compression for the first 3 days in the hospital after the surgery, the occurrence rate of stasis was lower than that of the active ankle pumping exercise without reminders, both in the hospital and at home. The same exercise was suggested for groups 1 and 2 at home after discharge, and the incidence of stasis was found to be 3.2% in group 2 and 17.2% in group 1 after the same exercises for 13 days. The \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Group 1**} & \multicolumn{2}{c}{**Group 2**} & \multicolumn{2}{c}{**Group 1**} & \multicolumn{2}{c}{**Total**} & \multicolumn{1}{c}{\(p\)} \\  & \multicolumn{2}{c}{**(N = 31)**} & \multicolumn{2}{c}{**(N = 29)**} & \multicolumn{2}{c}{**(N = 30)**} & \multicolumn{2}{c}{**Total**} & \multicolumn{1}{c}{\(p\)} \\ \cline{2-9}  & **Patient** & **\%** & **Patient** & **\%** & **Patient** & **\%** & **Patient** & **\%** & \\ \hline \hline \multicolumn{9}{c}{**Nonoperative limb**} & \multicolumn{2}{c}{0.294} \\ Stasis (\(-\)) & 25 & 86.2\% & 29 & 93.5\% & 29 & 96.7\% & 83 & 92.2\% & \\ Stasis (\(+\)) & 4 & 13.8\% & 2 & 6.5\% & 1 & 3.3\% & 7 & 7.8\% & \\
**3 rd day** & & & & & & & & \\ Stasis (\(-\)) & 24 & 82.8\% & 29 & 93.5\% & 29 & 96.7\% & 82 & 91.1\% & \\ Stasis (\(+\)) & 5 & 17.2\% & 2 & 6.5\% & 1 & 3.3\% & 8 & 8.9\% & \\
**14 th day** & & & & & & & & \\ Stasis (\(-\)) & 20 & 69.0\% & 29 & 93.5\% & 29 & 96.7\% & 78 & 86.7\% & \\ Stasis (\(+\)) & 9 & 31.0\% & 2 & 6.5\% & 1 & 3.3\% & 12 & 13.3\% & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: _Cont._reason for this is unknown, because the difference in exercise performance between the two groups is unknown.