I took a hard fall on the side walk, landing on my left knee. I did not have pain in my left knee before, but now I have pain in the left knee. Sometimes I have a throbbing sensation. Also if I sit to long that knee becomes very stiff, and in the back of my knee it becomes very hard, at times it is hard to squat or bend that knee. There is no similar pain in the right knee. Could the fall have anything to do with what I m experiencing . I had x-ray done and it says there is a elliptical shaped scierotic lesion in the left thigh of the left femur. What should I be dong at this point. Thank You.