HI,I suddenly started to have really sharp pain in my right knee. I have experienced some pain in the last few months in this knee when walking on stairs, and some grinding, but nothing major, pain lost only a few moments. Today, I can bend my knee with no pain in a sitting position, but when I bend it and put pressure on it (getting up) a very sharp pain goes through my knee. Lately, I have run more and exercised more than normal.