[Lucky]

CVs make a tick-tick-tick sound (that gets faster with speed and then tends to go away at higher speeds) as they start to go, not what I would call a knocking sound -- but we all use words differently, so maybe that's what it is. If you ignore that for too long you may get a more meaty knock just before catastrophic failure.

It's very easy to diagnose CVs by feel. Just crawl under the car, grab the 1/2 shaft in the middle of it's length and slide the half shaft in/out (that is towards and away from the tranny flange) and see if it moves smoothly and is well damped by grease. If you feel any roughness then you've got problems. If it moves too easily, but still feels smooth then you need grease, but should be damage free -- and in this case doesn't explain your knocking sound. Check both sides to compare feel. Since you have no noise on the driver side, I'd start there so you can learn what CVs should feel like first.

If you are a complete n00b it may be best to take to a shop. CV (and/or suspension) failure can be a safety concern, so it would be $ well spent if you aren't sure how to diagnose.

Good luck.