So, now we know it''s not going to be fixed for free by vx we can start asking q's to get the invest going.
1. Does the knocking noise occur when rotating the steering wheel with engine on?
2. Does the same happen for when the engine off (bit difficult to do without the power steering but give it a go)?
3. Does it occur at full lock only or is it all the way through the rotation?
4. Does it sound as though it is coming from directly in front of you or from the passenger side?
If you get to answer these we may be able to give you a bit more help, but without seeing and testing the vehicle it will be difficult to answer accurately.