Are you used to running? have you built up speed and distance gradually?
I used to run long distance, i then dislocated my knee, followed by damage in a car crash, my knee is almost metal lol. Ive not long got back into running and im trying to build things up gradually, i also find running on lower impact surfaces helps(such as grass rather than roads or treadmill) and also a good pair of running trainers with good cushioning helps loads.
Im being carefull to build up gradually, the last bit of damage i did to my knee was just over a year ago and i only started running a couple of weeks ago..so far so good. Im also swimming lots as i find this helps keep it loose, and im listening to my body..when it starts to ache or become sore, i change what im doing and stop running until its improved.
I also take glucosomine(sp?) and cod liver oil, and always wear a support wrap on the bad knee.
Life is not measured by the number of breaths we take, but by the moments that take our breath away.