I have pain radiating from my thigh down under my knee the pain has been there for 2 weeks since i took a knee to the thigh what could this be?

KNEE PAIN: 1) Is the pain constant ?Are you able to walk without problems? Any pain relief if lying down? 2) Any swelling , + if so, where and is there discoloration? Could be : pinched nerve ;fluid +/or blood leaking from bruised thigh; if swelling , discoloration behind knee, could be phlebitis /blood clot; or possible strain of cartilage of knee from trauma of leg. Have you treated it with ice or hat?