Christopher Ellis explains ankle pumps, a post-surgery exercise that prevents blood clots by moving blood out of the calves. Point and flex your feet 30 to 50 times per set, several times daily, with legs elevated. It's not about strength, just circulation.
These are called ankle pumps. This is not for strength, this is for circulation, particularly for blood, but it also helps with the lymph. After surgery, you're at increased risk for a DVT or a blood clot because you're more sedentary at this time frame, and blood is going to pool towards your calves where clots can form. So you can do this seated, in any position really, but it's best to do this with your legs elevated so you can take advantage of gravity. And you want to go high rep, 30, 40, 50 reps. You can do this multiple times a day.