Not by themselves. Blood clots can be caused by genetics, age, and other lifestyle factors. Under certain circumstances, wearing a knee sleeve could constrict some of the deep veins in your knee, causing deep vein thrombosis. This could happen if these 3 factors are involved at the same time: The sleeve is way too tight and uncomfortable. But still, you wear it for hours. While having your knee bent most of the time. This is an unlikely scenario that can be easily prevented if you wear the proper size of the knee sleeve and remove it if you feel uncomfortable. Remove it immediately and check with your physician if you feel any of the following: Your feet/calves tingling, numbing, etc. Your feet/calves are colder or warmer than usual. Impaired sensation below the knee sleeve. Pain on your feet/calves that increases while wearing the sleeve.