i honetsly think they do get cramps - when elmo was a new pup he used to just be sat still and all of a sudden would cry out in pain and lick his leg. Or it would happen when he was walking, running, asleep etc. At first it really worried me, thinking something had happened to him while i wasnt watching and he was really ill, but i honestly think it was cramp. It was something he grew out of quite quickly and i haven't seen it happen for at least 4 months.