Power steering

I have a 2002 Dodge Grand Caravan Sport. When I turn the steering wheel the car makes a creaking sound. It has power steering and I was wondering if anyone knew why??

I also have an 02 Caravan Sport. I had it in to the dealer SIX times for a grinding noise coming from the power steering system. Only this last time did they finally replace the PS pump, hoses and reservoir. Seems to be fixed now, but we'll know better in the next couple weeks.