What Causes Burning/tingling Sensation In Leg?

i have a burning , kinda a numbness tingling sensation on my left leg now for about a yr or so it is located right under my knee to the outside of the leg there is also a slight swelling the size of a half dollar also my feet feel so tight and hurt anf have the same senastion sometimes so bad it hurts to walk this is an all day feeling what might be the cause of this all??