I have a burning sensation and numbness on my upper left leg. There is no swelling or discoloring. I've had this before for short periods of time. I have put on extra weight ( 30lbs ) and since then I've had some back ache. I do a lot of standing for work, up to five hours on my feet, and it usually goes away after I sit or lie down but in the last week it seems to be getting worse. I am a 61 year old male with two open heart surgeries, Triple bypass and Aortic valve replacement in the last seven years. I also have a history of sciatica. Is this related to a nerve disorder or blood clot?