Ok...ive noticed a knocking (midrange sound) everytime im parked and move my steering wheel back and forth.

I jacked up the car and took off the wheel and nothing i could see was wrong however, the steering shaft that connects to the susp. has this ball join with a stud comin down. There's a lug nut on it from beneath. This lug nut twists everytime i turn the wheel. On the other side of the car it doesnt. The nut on the side that doesnt turn has 7 threads from the bottom before where the nut is. The driver side (the bad side) has 4. I cant tigthen it at ALL. When i try , the entire thing spins.

Would this cause the knocking sound, is it dangerous (most likely) and can i fix it.

any help would be greatly appreciated.

Thanks
C