What Causes Bruises And Pain On The Thigh?

I am 26, 125lbs, 5'6" and no history of health problems. For about the last 6 months or so I have been experiencing unexplained pain in my right thigh above the knee towards the side of my leg. Tender to the touch and feels like bruising. Bruises eventually show up all over my thighs. Sometimes the pain is on the back of my lower thigh and the bruises develop. The pain is mostly tenderness and develops into full on brusied type pain. It's starting to concern me because I am not hitting and/or bumping my leg on anything and they just show up!