Since last fall feel like my left leg is going numb especially from the knee down i get sharp pain shortly after commencing running and it freezes my leg from knee down while upper part of leg is stiff, right leg is normal. I may have initially injured this running down hill two years ago when car turned right in front of me and had to break hard on the left leg and could not continue run that day nor could run for a few days. Tried biking for several minutes last week and it quickly became sore then painful. I can crosscountry ski for 2-3 hours till snow went few weeks ago and swim easily 40 minutes and walk few hours no problem I think it is the angle of running and biking that makes pain. WHat is it and what can I do. Am a competitive runner age 57.