front driver wheel knocking sound

If it doesn't make a noise on turns the half shafts are unlikely to be a problem. A "knocking sound" at a certain speed if not accelerating is hard to understand as it wouldn't be brake related either. It is hard to say with out being able to experience the problem first hand, or be able to drive the vehicle and experience the problem and carry out some basic tests but it sounds like this is a matter that requires investigating really soon.