general problems of the 2004 Porsche Cayenne

I heard some knocking from the area of the front left wheel while driving on a city street about 30 miles per hour. I stopped and inspected under the car and saw nothing. So I decoded to bring it to my service provider. I drove about 3 miles at slow speeds to get to the service provider. After about an hour they found the problem. One of the bolts that holds the knuckle to the wheel had backed out and was banging around the break system. They said I could not drive the car until it was fixed.