"Another thing to look at is your wheelchair, if you use one. Is your wheelchair properly fitted to you or one "off the rack"? You need to make sure that your leg to footrest distance is short enough that there is minimal pressure at the back of the lower thigh and knee. Having your legs "dangle" (on any chair) can surely cause circulation problems. Try raising your footrests an inch or so. If you have added a wheelchair cushion since the footrest height was set, you need to adjust it to make up for the height of the cushion."

http://www.lindacrabtree.com/cmtnews/Feet/Feet4.htm

I would definately let your doctor know and get checked for clots. We don't want any thrombosis or nothing!