While standing for too long can be an issue, so can sitting. Some experts theorize that even sitting for extended periods can contribute to the development of varicose veins. The theory is that the bending of knees and hips will slow the return of blood to the heart. So, it is important to routinely move the legs during any long car ride, plane ride, or sitting at a desk.
While sitting can create greater pressure in the lower extremities, crossing your legs will slow the circulation even further. If legs want to be crossed, they should be crossed at the ankles only. Crossing at the knees not only causes increased pressure and increases the risk of closing the veins, but it also negatively impacts any problems with the knees and hips.