Hi, i was out on my bike today and i was riding down the road and all of a sudden my crank arm came loose and fell off. 
why might this of happend. 
I checked the bb, crank and bolt to see if anything was rounded of or if the threads had pulled out but they were fine. 
I have put lock tight on the bolt and put it back on should this stop it from happening again and why might this of happened ?