near the knuckle
US /nɪr ðə ˈnʌkəl/
UK /nɪr ðə ˈnʌkəl/

1.
きわどい, 下品な, 不適切な
almost offensive or rude, especially because of being sexual or involving rude humor
:
•
His jokes were a bit near the knuckle for the family gathering.
彼のジョークは家族の集まりには少しきわどかった。
•
The comedian's routine was quite near the knuckle, but the audience loved it.
そのコメディアンのネタはかなりきわどかったが、観客はそれを気に入った。