Recently For About The Past Two Week I Have Experienced

Recently for about the past two week I have experienced extreme pain in my left leg. The pain is very sensitive to the touch. like a burning sensation when I touch it. The pain around the knee cap area is like a throbbing pain and sometime on a consistant bases, it feels like someone is stabbing me in my knee. On some days I can barely stand to walk on it. The pain is getting more and more intense. There is never a sense of numness, just the feel of burning, or when i touch any of the areas on my leg I get that same burning feeling. I am experiencing these pains during the day, at night, even when I sleep. Please advise.
Thanks...