Pictures?
Depending on the knife, I'd probably scrub them with a nylon brush in (lightly) soapy water. Rinse & dry, then see how they look.
You can always hit them with steel wool or sandpaper (wear a good mask - you don't want to breathe that stuff); and hand buff with a polishing compound, if desired.
If the phenolic is more plastic-y, I don't know that I'd go the steel wool or sandpaper route - it would probably be pretty tough to buff out the scratches manually