What Causes Purple Discoloration Above My Knee Caps While Having Hypertension, Cholesterol, Poor Blood Circulation, Obesity, And Smoking Habit?

Hi i was inquiring about the skin just above my knee caps, 6 inches radios is purple, i did not bang them , but i know i am overweight and i dont exsersise much and i got bad /not much blood flow , I have high blood pressure ,high colesterol , and i am on the vurge of being a diabetic and i smoke over a pack a day sometimes 2 packs. i weighed 325 lbs 6 months ago ,and i said to myself its do or die ! i even lost a 29 year old niece 3 years ago cause she weighed 350 and her heart let go.