a really anoying knock

I think all 4G civics have that noise... if it's under the dead pedal on the driver side don't worry about it almost all Civics have that. It could be your bushings, primarily the lower shock where it mounts to the control arm, Energy Sus or Prothane has kits for the car $120-150, highly doubt it but maybe one of your engine mounts is loose or the rubber is torn. Probably the bushings would be my guess.