what cause a problem with the upper suspension arm rear both side ? on 2005 Audi A4

I've got a Audi A4 1.8 T s-line petrol 2005 . my two tires on the back , they are wear inside . my garage told me , I need to change the upper suspension arms . but could you explain me what is the cause of that problem with the upper ? thank you

2 answers 2 comments
This wil have to be inspected to determin the reason for replacement. If your "garage" did not explain it to you, like they should have, take your car to an alignment shop for further inspection and evaluation of your problem. Hopefully you will get an explanation. If not, it's your money, ask!
Thank you
poss rubber bushings are cracked and falling apart causing improper angle of tire
Went to the garage they don't find nothing wrong with the upper suspension arm .the cause of my tires wear inside it's because I drove on low tires pressure .