I hurt my knee about two months ago playing softball. I think I twisted it when I was fielding a ball. Initially I felt pain, but was able to keep playing. Later on, my knee felt stiff and I was unable to straightnen it. I have played the whole season without any serious problems. After all this time, my knee is still stiff and sometimes too painful to straighten, but lately have been able to straighten it out more than usual, although not quite completely. Also, the pain is not as severe as it used to be. It seems to be most bothersome after being on it for a long period of time. It does not lock or catch, but sometimes straightens out unexpectedly, which can be very painful. Do you have any ideas as to what could be wrong? Is it serious enough to go to the doctor about it?