What Causes Swelling & Numbness In The Legs & Knees?

Hi there What may be causing this?
Sypmtoms- swollen Legs,knee areas and area below the knee-apparent are bruising at the surface of the skn below my knees-my legs feel weak,heavy and numb at times and sometimes i feel throbbing and immense pain.. what could this be -any help would be grateful. thank you