Yes, the Knaack club is still alive, but the last time I've been there has been long ago (I'd say 3 or 4 years ago). Now it's mostly hiphop stuff over there or some crossover. I can remember the good ole industrial nights in the basement of this club, called "Darmwäsche" (intestinal cleaning). In fact it has been a butcher's shop long before the wall came down, that's for the name "Darmwäsche"...
Anyway, those times are gone and there are better clubs now. One of the old school punk clubs still is SO36 in Kreuzberg. Too bad they closed the Trash, it was a nice disco/club/bar which played music from all of the good cultures (indie, punk, wave, goth and metal), but SO36 is still alive!
When I say a few years ago, it was 1993 (13 years ago), we went with the band "Chelsea" went all round Germany with them when they were touring there, we got into all there gigs for free, got all our drink for free, they let us stay in their hotels for free, a great bunch of lads, they really looked after us.
Also went back with them in 1994 when they toured but didn't do Berlin that time so I've seen more of Germany than any other country (well apart from Britain)
Sorry, but I don't think that I know the band Chelsea. But I can tell you that Berlin has changed a lot in the last ten years, it might be worth a trip. :)