Boy, it could just be his personality. I have lived with 9 cats in my lifetime and all but 1 calmed down once they hit a year or so of age. But our Chase is 3 and still just as bonkers as he was when we found him ~4 months of age. He likes to ambush our ankles, too. Luckily, he doesn't use our claws when he does this, but he comes close to tripping us on a nearly daily basis.

How old is the little adoptee? Could be that he's still not calmed-down, yet.