Steering clunking sound

It would be good if you could make a short video of the noise and upload it with your response so I can see what's going on. But I would start by checking the tires to make sure they are tight (lug nuts) Next if the noise is coming from under the car it can be a loose steering rack, if the noise seems to be closer to the steering wheel the power motor that assists the steering system could have a broken gear on it.

The sounds only happens when you are stopped because the steering system puts the most pressure on it when the car is not moving. I have included the steering system diagrams below so you can see what I am talking about and how the system works. Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.