Suggest Treatment For Severe Knee Pain

hi, i am 53 year old woman and i've never had problem with my knees in my life. I had liposuctin 3 times in my belly, and one on my inner thighs. I have gain some weight, about 15 pounds through the years, but now i notice my knees hurt so bad when i stand up after sitting for a few hours (surfing in internet). I tried to exerise but i am afraid of running or jumping on my knee. i do stretching but my knee limits me. Should i be concern.