What Causes Constant Arm Pain?

hi.good day.i'm mike.i'm suffering left ar pain.i already take medicine,pain reliever but it still occur from time to time. i sufferig from this pain since last year 2010 july.i want to have a idea what is this?i play basketball but i dont remember any situation during i played that wll caused this problem.i'm 45 yrs old.pls. advise me.tnx..