It's usually at the end of the day, & sometimes during the night. It seems to be around his knee & down his shin. He is a very very active little boy (he's 4.8) so maybe it's something like lactic acid build-up? When I was little, & right up to my 30s, I used to get excruciating aches in my lower legs which my parents & childhood GP dismissed as 'growing pains' Do you think DS1 is 'just' suffering from these, or could it be something more serious? (I keep thinking cancer). He's well otherwise, just overtired 'cause he gets up too early every morning. I generally give him a dose of neurofen when he complains about it (the pain) which seems to ease it. What do you all think?